Mercurial > vim
annotate runtime/doc/vim9.txt @ 29263:8408ffd9af69 v8.2.5150
patch 8.2.5150: read past the end of the first line with ":0;'{"
Commit: https://github.com/vim/vim/commit/f7c7c3fad6d2135d558f3b36d0d1a943118aeb5e
Author: Bram Moolenaar <Bram@vim.org>
Date: Wed Jun 22 19:08:38 2022 +0100
patch 8.2.5150: read past the end of the first line with ":0;'{"
Problem: Read past the end of the first line with ":0;'{".
Solution: When on line zero check the column is valid for line one.
author | Bram Moolenaar <Bram@vim.org> |
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date | Wed, 22 Jun 2022 20:15:03 +0200 |
parents | 2a1f9b4a5ac9 |
children | 0fdf36de4018 |
rev | line source |
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29121 | 1 *vim9.txt* For Vim version 8.2. Last change: 2022 Jun 10 |
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2 |
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3 |
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4 VIM REFERENCE MANUAL by Bram Moolenaar |
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5 |
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6 |
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7 Vim9 script commands and expressions. *Vim9* *vim9* |
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8 |
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9 Most expression help is in |eval.txt|. This file is about the new syntax and |
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10 features in Vim9 script. |
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11 |
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12 |
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13 |
23466 | 14 1. What is Vim9 script? |Vim9-script| |
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15 2. Differences |vim9-differences| |
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16 3. New style functions |fast-functions| |
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17 4. Types |vim9-types| |
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18 5. Namespace, Import and Export |vim9script| |
22328 | 19 6. Future work: classes |vim9-classes| |
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20 |
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21 9. Rationale |vim9-rationale| |
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22 |
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23 ============================================================================== |
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24 |
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25 1. What is Vim9 script? *Vim9-script* |
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26 |
20241 | 27 Vim script has been growing over time, while preserving backwards |
28 compatibility. That means bad choices from the past often can't be changed | |
20965 | 29 and compatibility with Vi restricts possible solutions. Execution is quite |
20241 | 30 slow, each line is parsed every time it is executed. |
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31 |
20241 | 32 The main goal of Vim9 script is to drastically improve performance. This is |
33 accomplished by compiling commands into instructions that can be efficiently | |
34 executed. An increase in execution speed of 10 to 100 times can be expected. | |
35 | |
36 A secondary goal is to avoid Vim-specific constructs and get closer to | |
37 commonly used programming languages, such as JavaScript, TypeScript and Java. | |
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38 |
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39 The performance improvements can only be achieved by not being 100% backwards |
20552 | 40 compatible. For example, making function arguments available in the |
41 "a:" dictionary adds quite a lot of overhead. In a Vim9 function this | |
42 dictionary is not available. Other differences are more subtle, such as how | |
43 errors are handled. | |
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44 |
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45 The Vim9 script syntax and semantics are used in: |
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46 - a function defined with the `:def` command |
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47 - a script file where the first command is `vim9script` |
22328 | 48 - an autocommand defined in the context of the above |
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49 - a command prefixed with the `vim9cmd` command modifier |
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50 |
23573 | 51 When using `:function` in a Vim9 script file the legacy syntax is used, with |
52 the highest |scriptversion|. However, this can be confusing and is therefore | |
53 discouraged. | |
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54 |
20241 | 55 Vim9 script and legacy Vim script can be mixed. There is no requirement to |
22328 | 56 rewrite old scripts, they keep working as before. You may want to use a few |
57 `:def` functions for code that needs to be fast. | |
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58 |
27537 | 59 :vim9[cmd] {cmd} *:vim9* *:vim9cmd* *E1164* |
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60 Evaluate and execute {cmd} using Vim9 script syntax and |
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61 semantics. Useful when typing a command and in a legacy |
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62 script or function. |
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63 |
27537 | 64 :leg[acy] {cmd} *:leg* *:legacy* *E1189* *E1234* |
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65 Evaluate and execute {cmd} using legacy script syntax and |
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66 semantics. Only useful in a Vim9 script or a :def function. |
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67 Note that {cmd} cannot use local variables, since it is parsed |
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68 with legacy expression syntax. |
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69 |
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70 ============================================================================== |
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71 |
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72 2. Differences from legacy Vim script *vim9-differences* |
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73 |
22441 | 74 Overview ~ |
27537 | 75 *E1146* |
22441 | 76 Brief summary of the differences you will most often encounter when using Vim9 |
77 script and `:def` functions; details are below: | |
78 - Comments start with #, not ": > | |
23573 | 79 echo "hello" # comment |
22441 | 80 - Using a backslash for line continuation is hardly ever needed: > |
23573 | 81 echo "hello " |
22441 | 82 .. yourName |
83 .. ", how are you?" | |
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84 - White space is required in many places to improve readability. |
27459 | 85 - Assign values without `:let` *E1126* , declare variables with `:var`: > |
23573 | 86 var count = 0 |
22441 | 87 count += 3 |
88 - Constants can be declared with `:final` and `:const`: > | |
29104 | 89 final matches = [] # add to the list later |
22441 | 90 const names = ['Betty', 'Peter'] # cannot be changed |
91 - `:final` cannot be used as an abbreviation of `:finally`. | |
92 - Variables and functions are script-local by default. | |
93 - Functions are declared with argument types and return type: > | |
94 def CallMe(count: number, message: string): bool | |
95 - Call functions without `:call`: > | |
23573 | 96 writefile(['done'], 'file.txt') |
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97 - You cannot use old Ex commands: |
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98 `:Print` |
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99 `:append` |
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100 `:change` |
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101 `:d` directly followed by 'd' or 'p'. |
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102 `:insert` |
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103 `:k` |
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104 `:mode` |
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105 `:open` |
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106 `:s` with only flags |
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107 `:t` |
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108 `:xit` |
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109 - Some commands, especially those used for flow control, cannot be shortened. |
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110 E.g., `:throw` cannot be written as `:th`. *E839* |
25973 | 111 - You cannot use curly-braces names. |
22441 | 112 - A range before a command must be prefixed with a colon: > |
23573 | 113 :%s/this/that |
25700 | 114 - Executing a register with "@r" does not work, you can prepend a colon or use |
115 `:exe`: > | |
116 :exe @a | |
23573 | 117 - Unless mentioned specifically, the highest |scriptversion| is used. |
27162 | 118 - When defining an expression mapping, the expression will be evaluated in the |
119 context of the script where it was defined. | |
22441 | 120 |
121 | |
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122 Comments starting with # ~ |
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123 |
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124 In legacy Vim script comments start with double quote. In Vim9 script |
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125 comments start with #. > |
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126 # declarations |
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127 var count = 0 # number of occurrences |
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128 |
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129 The reason is that a double quote can also be the start of a string. In many |
21825 | 130 places, especially halfway through an expression with a line break, it's hard |
131 to tell what the meaning is, since both a string and a comment can be followed | |
132 by arbitrary text. To avoid confusion only # comments are recognized. This | |
133 is the same as in shell scripts and Python programs. | |
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134 |
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135 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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136 `:number` for that. > |
27036 | 137 :101 number |
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138 |
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139 To improve readability there must be a space between a command and the # |
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140 that starts a comment: > |
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141 var name = value # comment |
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142 var name = value# error! |
27537 | 143 < *E1170* |
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144 Do not start a comment with #{, it looks like the legacy dictionary literal |
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145 and produces an error where this might be confusing. #{{ or #{{{ are OK, |
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146 these can be used to start a fold. |
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147 |
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148 In legacy Vim script # is also used for the alternate file name. In Vim9 |
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149 script you need to use %% instead. Instead of ## use %%% (stands for all |
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150 arguments). |
20115 | 151 |
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152 |
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153 Vim9 functions ~ |
27459 | 154 *E1099* |
20241 | 155 A function defined with `:def` is compiled. Execution is many times faster, |
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156 often 10 to 100 times. |
20241 | 157 |
20552 | 158 Many errors are already found when compiling, before the function is executed. |
20241 | 159 The syntax is strict, to enforce code that is easy to read and understand. |
160 | |
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161 Compilation is done when any of these is encountered: |
23164 | 162 - the first time the function is called |
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163 - when the `:defcompile` command is encountered in the script after the |
21991 | 164 function was defined |
165 - `:disassemble` is used for the function. | |
166 - a function that is compiled calls the function or uses it as a function | |
25700 | 167 reference (so that the argument and return types can be checked) |
27537 | 168 *E1091* *E1191* |
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169 If compilation fails it is not tried again on the next call, instead this |
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170 error is given: "E1091: Function is not compiled: {name}". |
24569 | 171 Compilation will fail when encountering a user command that has not been |
172 created yet. In this case you can call `execute()` to invoke it at runtime. > | |
173 def MyFunc() | |
174 execute('DefinedLater') | |
175 enddef | |
20552 | 176 |
177 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
23164 | 178 "closure". A `:def` function always aborts on an error (unless `:silent!` was |
26708 | 179 used for the command or the error was caught a `:try` block), does not get a |
29104 | 180 range passed, cannot be a "dict" function, and can always be a closure. |
25700 | 181 *vim9-no-dict-function* |
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182 Later classes will be added, which replaces the "dict function" mechanism. |
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183 For now you will need to pass the dictionary explicitly: > |
29104 | 184 def DictFunc(self: dict<any>, arg: string) |
185 echo self[arg] | |
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186 enddef |
28246 | 187 var ad = {item: 'value', func: DictFunc} |
28379 | 188 ad.func(ad, 'item') |
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189 |
25836 | 190 You can call a legacy dict function though: > |
191 func Legacy() dict | |
192 echo self.value | |
193 endfunc | |
194 def CallLegacy() | |
195 var d = {func: Legacy, value: 'text'} | |
196 d.func() | |
197 enddef | |
27537 | 198 < *E1096* *E1174* *E1175* |
20241 | 199 The argument types and return type need to be specified. The "any" type can |
200 be used, type checking will then be done at runtime, like with legacy | |
201 functions. | |
27459 | 202 *E1106* |
21825 | 203 Arguments are accessed by name, without "a:", just like any other language. |
204 There is no "a:" dictionary or "a:000" list. | |
27537 | 205 *vim9-variable-arguments* *E1055* *E1160* *E1180* |
20241 | 206 Variable arguments are defined as the last argument, with a name and have a |
21825 | 207 list type, similar to TypeScript. For example, a list of numbers: > |
22171 | 208 def MyFunc(...itemlist: list<number>) |
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209 for item in itemlist |
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210 ... |
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211 |
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212 When a function argument is optional (it has a default value) passing `v:none` |
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213 as the argument results in using the default value. This is useful when you |
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214 want to specify a value for an argument that comes after an argument that |
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215 should use its default value. Example: > |
25973 | 216 def MyFunc(one = 'one', last = 'last') |
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217 ... |
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218 enddef |
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219 MyFunc(v:none, 'LAST') # first argument uses default value 'one' |
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220 < |
27537 | 221 *vim9-ignored-argument* *E1181* |
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222 The argument "_" (an underscore) can be used to ignore the argument. This is |
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223 most useful in callbacks where you don't need it, but do need to give an |
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224 argument to match the call. E.g. when using map() two arguments are passed, |
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225 the key and the value, to ignore the key: > |
29104 | 226 map(numberList, (_, v) => v * 2) |
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227 There is no error for using the "_" argument multiple times. No type needs to |
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228 be given. |
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229 |
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230 |
20241 | 231 Functions and variables are script-local by default ~ |
20856 | 232 *vim9-scopes* |
20115 | 233 When using `:function` or `:def` to specify a new function at the script level |
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234 in a Vim9 script, the function is local to the script. Like prefixing "s:" in |
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235 legacy script. To define a global function or variable the "g:" prefix must |
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236 be used. For functions in a script that is to be imported and in an autoload |
29104 | 237 script "export" needs to be used for those to be used elsewhere. > |
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238 def ThisFunction() # script-local |
22171 | 239 def g:ThatFunction() # global |
27623 | 240 export def Function() # for import and import autoload |
27321 | 241 < *E1058* *E1075* |
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242 When using `:function` or `:def` to specify a nested function inside a `:def` |
26438 | 243 function and no namespace was given, this nested function is local to the code |
27903 | 244 block it is defined in. It cannot be used in `function()` with a string |
245 argument, pass the function reference itself: > | |
246 def Outer() | |
247 def Inner() | |
248 echo 'inner' | |
249 enddef | |
250 var Fok = function(Inner) # OK | |
251 var Fbad = function('Inner') # does not work | |
252 | |
29104 | 253 Detail: this is because "Inner" will actually become a function reference to a |
254 function with a generated name. | |
255 | |
256 It is not possible to define a script-local function in a function. You can | |
257 define a local function and assign it to a script-local funcref (it must have | |
258 been declared at the script level). It is possible to define a global | |
259 function by using the "g:" prefix. | |
20115 | 260 |
261 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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262 search for the function: |
22565 | 263 - in the function scope, in block scopes |
29104 | 264 - in the script scope |
265 | |
266 Imported functions are found with the prefix from the `:import` command. | |
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267 |
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268 Since a script-local function reference can be used without "s:" the name must |
24278 | 269 start with an upper case letter even when using the "s:" prefix. In legacy |
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270 script "s:funcref" could be used, because it could not be referred to with |
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271 "funcref". In Vim9 script it can, therefore "s:Funcref" must be used to avoid |
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272 that the name interferes with builtin functions. |
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273 *vim9-s-namespace* |
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274 The use of the "s:" prefix is not supported at the Vim9 script level. All |
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275 functions and variables without a prefix are script-local. |
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276 |
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277 In :def functions the use of "s:" depends on the script: Script-local |
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278 variables and functions in a legacy script do use "s:", while in a Vim9 script |
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279 they do not use "s:". This matches what you see in the rest of the file. |
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280 |
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281 In legacy functions the use of "s:" for script items is required, as before. |
29104 | 282 No matter if the script is Vim9 or legacy. |
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283 |
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284 In all cases the function must be defined before used. That is when it is |
22723 | 285 called, when `:defcompile` causes it to be compiled, or when code that calls |
286 it is being compiled (to figure out the return type). | |
20241 | 287 |
21676 | 288 The result is that functions and variables without a namespace can usually be |
20241 | 289 found in the script, either defined there or imported. Global functions and |
29104 | 290 variables could be defined anywhere (good luck finding out where! You can |
291 often see where it was last set using |:verbose|). | |
27459 | 292 *E1102* |
21825 | 293 Global functions can still be defined and deleted at nearly any time. In |
20317 | 294 Vim9 script script-local functions are defined once when the script is sourced |
29104 | 295 and cannot be deleted or replaced by itself (it can be by reloading the |
296 script). | |
20115 | 297 |
23305 | 298 When compiling a function and a function call is encountered for a function |
299 that is not (yet) defined, the |FuncUndefined| autocommand is not triggered. | |
300 You can use an autoload function if needed, or call a legacy function and have | |
301 |FuncUndefined| triggered there. | |
302 | |
20115 | 303 |
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304 Reloading a Vim9 script clears functions and variables by default ~ |
27537 | 305 *vim9-reload* *E1149* *E1150* |
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306 When loading a legacy Vim script a second time nothing is removed, the |
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307 commands will replace existing variables and functions, create new ones, and |
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308 leave removed things hanging around. |
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309 |
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310 When loading a Vim9 script a second time all existing script-local functions |
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311 and variables are deleted, thus you start with a clean slate. This is useful |
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312 if you are developing a plugin and want to try a new version. If you renamed |
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313 something you don't have to worry about the old name still hanging around. |
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314 |
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315 If you do want to keep items, use: > |
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316 vim9script noclear |
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317 |
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318 You want to use this in scripts that use a `finish` command to bail out at |
27804 | 319 some point when loaded again. E.g. when a buffer local option is set to a |
320 function, the function does not need to be defined more than once: > | |
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321 vim9script noclear |
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322 setlocal completefunc=SomeFunc |
27804 | 323 if exists('*SomeFunc') |
27623 | 324 finish |
325 endif | |
27804 | 326 def SomeFunc() |
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327 .... |
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328 |
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329 |
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330 Variable declarations with :var, :final and :const ~ |
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331 *vim9-declaration* *:var* *E1079* |
27459 | 332 *E1017* *E1020* *E1054* *E1087* *E1108* *E1124* |
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333 Local variables need to be declared with `:var`. Local constants need to be |
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334 declared with `:final` or `:const`. We refer to both as "variables" in this |
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335 section. |
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336 |
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337 Variables can be local to a script, function or code block: > |
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338 vim9script |
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339 var script_var = 123 |
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340 def SomeFunc() |
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341 var func_var = script_var |
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342 if cond |
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343 var block_var = func_var |
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344 ... |
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345 |
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346 The variables are only visible in the block where they are defined and nested |
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347 blocks. Once the block ends the variable is no longer accessible: > |
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348 if cond |
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349 var inner = 5 |
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350 else |
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351 var inner = 0 |
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352 endif |
22171 | 353 echo inner # Error! |
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354 |
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355 The declaration must be done earlier: > |
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356 var inner: number |
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357 if cond |
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358 inner = 5 |
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359 else |
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360 inner = 0 |
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361 endif |
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362 echo inner |
29104 | 363 |
364 Although this is shorter and faster for simple values: > | |
365 var inner = 0 | |
366 if cond | |
367 inner = 5 | |
368 endif | |
369 echo inner | |
27459 | 370 < *E1025* *E1128* |
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371 To intentionally hide a variable from code that follows, a block can be |
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372 used: > |
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373 { |
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374 var temp = 'temp' |
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375 ... |
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376 } |
22171 | 377 echo temp # Error! |
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378 |
25402 | 379 This is especially useful in a user command: > |
380 | |
381 command -range Rename { | |
25619 | 382 var save = @a |
383 @a = 'some expression' | |
384 echo 'do something with ' .. @a | |
385 @a = save | |
386 } | |
25402 | 387 |
388 And with autocommands: > | |
389 | |
390 au BufWritePre *.go { | |
25619 | 391 var save = winsaveview() |
392 silent! exe ':%! some formatting command' | |
393 winrestview(save) | |
394 } | |
25402 | 395 |
396 Although using a :def function probably works better. | |
28246 | 397 |
27537 | 398 *E1022* *E1103* *E1130* *E1131* *E1133* |
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399 *E1134* |
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400 Declaring a variable with a type but without an initializer will initialize to |
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401 false (for bool), empty (for string, list, dict, etc.) or zero (for number, |
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402 any, etc.). This matters especially when using the "any" type, the value will |
28246 | 403 default to the number zero. For example, when declaring a list, items can be |
404 added: > | |
405 var myList: list<number> | |
406 myList->add(7) | |
407 | |
408 Initializing a variable to a null value, e.g. `null_list`, differs from not | |
409 initializing the variable. This throws an error: > | |
410 var myList = null_list | |
411 myList->add(7) # E1130: Cannot add to null list | |
412 | |
413 < *E1016* *E1052* *E1066* | |
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414 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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415 without any command. The same for global, window, tab, buffer and Vim |
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416 variables, because they are not really declared. Those can also be deleted |
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417 with `:unlet`. |
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418 *E1065* |
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419 You cannot use `:va` to declare a variable, it must be written with the full |
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420 name `:var`. Just to make sure it is easy to read. |
27537 | 421 *E1178* |
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422 `:lockvar` does not work on local variables. Use `:const` and `:final` |
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423 instead. |
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424 |
25619 | 425 The `exists()` and `exists_compiled()` functions do not work on local variables |
426 or arguments. | |
27537 | 427 *E1006* *E1041* *E1167* *E1168* *E1213* |
24024 | 428 Variables, functions and function arguments cannot shadow previously defined |
429 or imported variables and functions in the same script file. | |
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430 Variables may shadow Ex commands, rename the variable if needed. |
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431 |
24387 | 432 Global variables must be prefixed with "g:", also at the script level. > |
19968 | 433 vim9script |
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434 var script_local = 'text' |
21499 | 435 g:global = 'value' |
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436 var Funcref = g:ThatFunction |
19968 | 437 |
27492 | 438 Global functions must be prefixed with "g:": > |
24387 | 439 vim9script |
440 def g:GlobalFunc(): string | |
441 return 'text' | |
442 enddef | |
27492 | 443 echo g:GlobalFunc() |
24387 | 444 The "g:" prefix is not needed for auto-load functions. |
445 | |
25619 | 446 *vim9-function-defined-later* |
447 Although global functions can be called without the "g:" prefix, they must | |
448 exist when compiled. By adding the "g:" prefix the function can be defined | |
449 later. Example: > | |
450 def CallPluginFunc() | |
451 if exists('g:loaded_plugin') | |
452 g:PluginFunc() | |
453 endif | |
454 enddef | |
455 | |
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456 If you do it like this, you get an error at compile time that "PluginFunc" |
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457 does not exist, even when "g:loaded_plugin" does not exist: > |
25619 | 458 def CallPluginFunc() |
459 if exists('g:loaded_plugin') | |
460 PluginFunc() # Error - function not found | |
461 endif | |
462 enddef | |
463 | |
464 You can use exists_compiled() to avoid the error, but then the function would | |
465 not be called, even when "g:loaded_plugin" is defined later: > | |
466 def CallPluginFunc() | |
467 if exists_compiled('g:loaded_plugin') | |
468 PluginFunc() # Function may never be called | |
469 endif | |
470 enddef | |
471 | |
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472 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
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473 used to repeat a `:substitute` command. |
24468 | 474 *vim9-unpack-ignore* |
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475 For an unpack assignment the underscore can be used to ignore a list item, |
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476 similar to how a function argument can be ignored: > |
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477 [a, _, c] = theList |
24468 | 478 To ignore any remaining items: > |
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479 [a, b; _] = longList |
27804 | 480 < *E1163* *E1080* |
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481 Declaring more than one variable at a time, using the unpack notation, is |
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482 possible. Each variable can have a type or infer it from the value: > |
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483 var [v1: number, v2] = GetValues() |
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484 Use this only when there is a list with values, declaring one variable per |
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485 line is much easier to read and change later. |
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486 |
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487 |
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488 Constants ~ |
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489 *vim9-const* *vim9-final* |
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490 How constants work varies between languages. Some consider a variable that |
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491 can't be assigned another value a constant. JavaScript is an example. Others |
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492 also make the value immutable, thus when a constant uses a list, the list |
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493 cannot be changed. In Vim9 we can use both. |
27321 | 494 *E1021* |
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495 `:const` is used for making both the variable and the value a constant. Use |
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496 this for composite structures that you want to make sure will not be modified. |
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497 Example: > |
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498 const myList = [1, 2] |
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499 myList = [3, 4] # Error! |
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500 myList[0] = 9 # Error! |
24024 | 501 myList->add(3) # Error! |
27459 | 502 < *:final* *E1125* |
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503 `:final` is used for making only the variable a constant, the value can be |
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504 changed. This is well known from Java. Example: > |
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505 final myList = [1, 2] |
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506 myList = [3, 4] # Error! |
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507 myList[0] = 9 # OK |
24024 | 508 myList->add(3) # OK |
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509 |
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510 It is common to write constants as ALL_CAPS, but you don't have to. |
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511 |
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512 The constant only applies to the value itself, not what it refers to. > |
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513 final females = ["Mary"] |
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514 const NAMES = [["John", "Peter"], females] |
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515 NAMES[0] = ["Jack"] # Error! |
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516 NAMES[0][0] = "Jack" # Error! |
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517 NAMES[1] = ["Emma"] # Error! |
23573 | 518 NAMES[1][0] = "Emma" # OK, now females[0] == "Emma" |
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519 |
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520 |
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521 Omitting :call and :eval ~ |
27537 | 522 *E1190* |
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523 Functions can be called without `:call`: > |
22171 | 524 writefile(lines, 'file') |
19303 | 525 Using `:call` is still possible, but this is discouraged. |
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526 |
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527 A method call without `eval` is possible, so long as the start is an |
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528 identifier or can't be an Ex command. For a function either "(" or "->" must |
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patch 8.2.2605: Vim9: string index and slice does not include composing chars
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529 be following, without a line break. Examples: > |
21516
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patch 8.2.1308: Vim9: accidentally using "x" causes Vim to exit
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530 myList->add(123) |
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531 g:myList->add(123) |
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532 [1, 2, 3]->Process() |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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533 {a: 1, b: 2}->Process() |
21516
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534 "foobar"->Process() |
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535 ("foobar")->Process() |
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536 'foobar'->Process() |
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537 ('foobar')->Process() |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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538 |
21825 | 539 In the rare case there is ambiguity between a function name and an Ex command, |
21676 | 540 prepend ":" to make clear you want to use the Ex command. For example, there |
541 is both the `:substitute` command and the `substitute()` function. When the | |
542 line starts with `substitute(` this will use the function. Prepend a colon to | |
543 use the command instead: > | |
19481
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patch 8.2.0298: Vim9 script: cannot start command with a string constant
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|
544 :substitute(pattern (replacement ( |
19473
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patch 8.2.0294: cannot use Ex command that is also a function name
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|
545 |
25402 | 546 If the expression starts with "!" this is interpreted as a shell command, not |
547 negation of a condition. Thus this is a shell command: > | |
548 !shellCommand->something | |
25700 | 549 Put the expression in parentheses to use the "!" for negation: > |
25402 | 550 (!expression)->Method() |
551 | |
19556
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patch 8.2.0335: no completion for :disassemble
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552 Note that while variables need to be defined before they can be used, |
21825 | 553 functions can be called before being defined. This is required to allow |
554 for cyclic dependencies between functions. It is slightly less efficient, | |
19556
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patch 8.2.0335: no completion for :disassemble
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555 since the function has to be looked up by name. And a typo in the function |
21516
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556 name will only be found when the function is called. |
19556
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patch 8.2.0335: no completion for :disassemble
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557 |
19181
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
558 |
19968 | 559 Omitting function() ~ |
560 | |
561 A user defined function can be used as a function reference in an expression | |
562 without `function()`. The argument types and return type will then be checked. | |
563 The function must already have been defined. > | |
564 | |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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565 var Funcref = MyFunction |
19968 | 566 |
567 When using `function()` the resulting type is "func", a function with any | |
25161 | 568 number of arguments and any return type (including void). The function can be |
26708 | 569 defined later if the argument is in quotes. |
19968 | 570 |
571 | |
23358
b3142fc0a414
patch 8.2.2222: Vim9: cannot keep script variables when reloading
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|
572 Lambda using => instead of -> ~ |
24387 | 573 *vim9-lambda* |
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574 In legacy script there can be confusion between using "->" for a method call |
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|
575 and for a lambda. Also, when a "{" is found the parser needs to figure out if |
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576 it is the start of a lambda or a dictionary, which is now more complicated |
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577 because of the use of argument types. |
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578 |
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579 To avoid these problems Vim9 script uses a different syntax for a lambda, |
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580 which is similar to JavaScript: > |
23318
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581 var Lambda = (arg) => expression |
27537 | 582 var Lambda = (arg): type => expression |
583 < *E1157* | |
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584 No line break is allowed in the arguments of a lambda up to and including the |
25056 | 585 "=>" (so that Vim can tell the difference between an expression in parentheses |
24911 | 586 and lambda arguments). This is OK: > |
23318
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587 filter(list, (k, v) => |
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588 v > 0) |
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589 This does not work: > |
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590 filter(list, (k, v) |
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591 => v > 0) |
23392
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592 This also does not work: > |
23318
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593 filter(list, (k, |
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594 v) => v > 0) |
23392
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595 But you can use a backslash to concatenate the lines before parsing: > |
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596 filter(list, (k, |
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597 \ v) |
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598 \ => v > 0) |
27537 | 599 < *vim9-lambda-arguments* *E1172* |
24408
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600 In legacy script a lambda could be called with any number of extra arguments, |
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601 there was no way to warn for not using them. In Vim9 script the number of |
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602 arguments must match. If you do want to accept any arguments, or any further |
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603 arguments, use "..._", which makes the function accept |
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diff
changeset
|
604 |vim9-variable-arguments|. Example: > |
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605 var Callback = (..._) => 'anything' |
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|
606 echo Callback(1, 2, 3) # displays "anything" |
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607 |
27537 | 608 < *inline-function* *E1171* |
23318
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609 Additionally, a lambda can contain statements in {}: > |
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610 var Lambda = (arg) => { |
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611 g:was_called = 'yes' |
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612 return expression |
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613 } |
24387 | 614 This can be useful for a timer, for example: > |
615 var count = 0 | |
616 var timer = timer_start(500, (_) => { | |
617 count += 1 | |
618 echom 'Handler called ' .. count | |
619 }, {repeat: 3}) | |
620 | |
24272
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621 The ending "}" must be at the start of a line. It can be followed by other |
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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622 characters, e.g.: > |
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623 var d = mapnew(dict, (k, v): string => { |
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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624 return 'value' |
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625 }) |
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626 No command can follow the "{", only a comment can be used there. |
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627 |
27321 | 628 *command-block* *E1026* |
26612
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patch 8.2.3835: the inline-function example does not work
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|
629 The block can also be used for defining a user command. Inside the block Vim9 |
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630 syntax will be used. |
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631 |
26591 | 632 If the statements include a dictionary, its closing bracket must not be |
633 written at the start of a line. Otherwise, it would be parsed as the end of | |
634 the block. This does not work: > | |
635 command NewCommand { | |
26612
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636 g:mydict = { |
26591 | 637 'key': 'value', |
638 } # ERROR: will be recognized as the end of the block | |
639 } | |
640 Put the '}' after the last item to avoid this: > | |
641 command NewCommand { | |
26612
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patch 8.2.3835: the inline-function example does not work
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|
642 g:mydict = { |
26591 | 643 'key': 'value' } |
644 } | |
645 | |
24272
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|
646 Rationale: The "}" cannot be after a command because it would require parsing |
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|
647 the commands to find it. For consistency with that no command can follow the |
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|
648 "{". Unfortunately this means using "() => { command }" does not work, line |
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649 breaks are always required. |
23318
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650 |
23737 | 651 *vim9-curly* |
23358
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652 To avoid the "{" of a dictionary literal to be recognized as a statement block |
24024 | 653 wrap it in parentheses: > |
23358
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654 var Lambda = (arg) => ({key: 42}) |
23318
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655 |
23737 | 656 Also when confused with the start of a command block: > |
657 ({ | |
658 key: value | |
659 })->method() | |
660 | |
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661 |
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
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662 Automatic line continuation ~ |
27459 | 663 *vim9-line-continuation* *E1097* |
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
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664 In many cases it is obvious that an expression continues on the next line. In |
23392
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|
665 those cases there is no need to prefix the line with a backslash (see |
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|
666 |line-continuation|). For example, when a list spans multiple lines: > |
22391
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667 var mylist = [ |
19999
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668 'one', |
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669 'two', |
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670 ] |
20011
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
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671 And when a dict spans multiple lines: > |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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672 var mydict = { |
20011
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673 one: 1, |
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674 two: 2, |
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675 } |
24888
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676 With a function call: > |
22391
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677 var result = Func( |
20011
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678 arg1, |
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679 arg2 |
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
680 ) |
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681 |
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682 For binary operators in expressions not in [], {} or () a line break is |
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683 possible just before or after the operator. For example: > |
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684 var text = lead |
20982
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685 .. middle |
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patch 8.2.1042: Vim9: cannot put an operator on the next line
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686 .. end |
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687 var total = start + |
23573 | 688 end - |
20013
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patch 8.2.0562: Vim9: cannot split an expression into multiple lines
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|
689 correction |
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690 var result = positive |
20982
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691 ? PosFunc(arg) |
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|
692 : NegFunc(arg) |
20013
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693 |
21499 | 694 For a method call using "->" and a member using a dot, a line break is allowed |
695 before it: > | |
22391
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|
696 var result = GetBuilder() |
20965 | 697 ->BuilderSetWidth(333) |
698 ->BuilderSetHeight(777) | |
699 ->BuilderBuild() | |
22391
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|
700 var result = MyDict |
21499 | 701 .member |
20965 | 702 |
23392
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
703 For commands that have an argument that is a list of commands, the | character |
517fca70e084
patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
704 at the start of the line indicates line continuation: > |
517fca70e084
patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
705 autocmd BufNewFile *.match if condition |
517fca70e084
patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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706 | echo 'match' |
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
707 | endif |
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|
708 |
25973 | 709 Note that this means that in heredoc the first line cannot start with a bar: > |
24888
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patch 8.2.2982: Vim9: future commands are not reserved yet
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710 var lines =<< trim END |
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711 | this doesn't work |
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|
712 END |
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|
713 Either use an empty line at the start or do not use heredoc. Or temporarily |
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|
714 add the "C" flag to 'cpoptions': > |
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patch 8.2.2982: Vim9: future commands are not reserved yet
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|
715 set cpo+=C |
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|
716 var lines =<< trim END |
25973 | 717 | this works |
24888
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|
718 END |
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|
719 set cpo-=C |
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changeset
|
720 If the heredoc is inside a function 'cpoptions' must be set before :def and |
b6ac4ed5e2d2
patch 8.2.2982: Vim9: future commands are not reserved yet
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|
721 restored after the :enddef. |
b6ac4ed5e2d2
patch 8.2.2982: Vim9: future commands are not reserved yet
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|
722 |
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723 In places where line continuation with a backslash is still needed, such as |
25161 | 724 splitting up a long Ex command, comments can start with '#\ ': > |
725 syn region Text | |
24888
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|
726 \ start='foo' |
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727 #\ comment |
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|
728 \ end='bar' |
25161 | 729 Like with legacy script '"\ ' is used. This is also needed when line |
730 continuation is used without a backslash and a line starts with a bar: > | |
731 au CursorHold * echom 'BEFORE bar' | |
732 #\ some comment | |
733 | echom 'AFTER bar' | |
734 < | |
735 *E1050* | |
20982
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|
736 To make it possible for the operator at the start of the line to be |
24888
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737 recognized, it is required to put a colon before a range. This example will |
b6ac4ed5e2d2
patch 8.2.2982: Vim9: future commands are not reserved yet
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|
738 add "start" and print: > |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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739 var result = start |
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740 + print |
21250 | 741 Like this: > |
22391
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742 var result = start + print |
21250 | 743 |
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patch 8.2.1042: Vim9: cannot put an operator on the next line
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744 This will assign "start" and print a line: > |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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|
745 var result = start |
20982
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patch 8.2.1042: Vim9: cannot put an operator on the next line
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746 :+ print |
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
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747 |
27321 | 748 After the range an Ex command must follow. Without the colon you can call a |
749 function without `:call`, but after a range you do need it: > | |
750 MyFunc() | |
751 :% call MyFunc() | |
752 | |
23047 | 753 Note that the colon is not required for the |+cmd| argument: > |
754 edit +6 fname | |
755 | |
20015
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patch 8.2.0563: Vim9: cannot split a function line
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|
756 It is also possible to split a function header over multiple lines, in between |
c001ee73519a
patch 8.2.0563: Vim9: cannot split a function line
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757 arguments: > |
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changeset
|
758 def MyFunc( |
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759 text: string, |
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760 separator = '-' |
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761 ): string |
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762 |
23305 | 763 Since a continuation line cannot be easily recognized the parsing of commands |
23318
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
764 has been made stricter. E.g., because of the error in the first line, the |
23305 | 765 second line is seen as a separate command: > |
766 popup_create(some invalid expression, { | |
767 exit_cb: Func}) | |
768 Now "exit_cb: Func})" is actually a valid command: save any changes to the | |
769 file "_cb: Func})" and exit. To avoid this kind of mistake in Vim9 script | |
770 there must be white space between most command names and the argument. | |
27459 | 771 *E1144* |
23305 | 772 |
23666 | 773 However, the argument of a command that is a command won't be recognized. For |
774 example, after "windo echo expr" a line break inside "expr" will not be seen. | |
775 | |
23305 | 776 |
21250 | 777 Notes: |
778 - "enddef" cannot be used at the start of a continuation line, it ends the | |
779 current function. | |
780 - No line break is allowed in the LHS of an assignment. Specifically when | |
781 unpacking a list |:let-unpack|. This is OK: > | |
22171 | 782 [var1, var2] = |
21250 | 783 Func() |
784 < This does not work: > | |
22171 | 785 [var1, |
21250 | 786 var2] = |
787 Func() | |
788 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
789 similar commands. This is OK: > | |
22171 | 790 echo [1, |
21250 | 791 2] [3, |
792 4] | |
793 < This does not work: > | |
22171 | 794 echo [1, 2] |
21250 | 795 [3, 4] |
24888
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changeset
|
796 - In some cases it is difficult for Vim to parse a command, especially when |
b6ac4ed5e2d2
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changeset
|
797 commands are used as an argument to another command, such as `windo`. In |
b6ac4ed5e2d2
patch 8.2.2982: Vim9: future commands are not reserved yet
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changeset
|
798 those cases the line continuation with a backslash has to be used. |
19999
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799 |
24569 | 800 |
801 White space ~ | |
27537 | 802 *E1004* *E1068* *E1069* *E1074* *E1127* *E1202* |
24569 | 803 Vim9 script enforces proper use of white space. This is no longer allowed: > |
804 var name=234 # Error! | |
805 var name= 234 # Error! | |
806 var name =234 # Error! | |
807 There must be white space before and after the "=": > | |
808 var name = 234 # OK | |
809 White space must also be put before the # that starts a comment after a | |
810 command: > | |
811 var name = 234# Error! | |
812 var name = 234 # OK | |
813 | |
814 White space is required around most operators. | |
815 | |
816 White space is required in a sublist (list slice) around the ":", except at | |
817 the start and end: > | |
818 otherlist = mylist[v : count] # v:count has a different meaning | |
819 otherlist = mylist[:] # make a copy of the List | |
820 otherlist = mylist[v :] | |
821 otherlist = mylist[: v] | |
822 | |
823 White space is not allowed: | |
824 - Between a function name and the "(": > | |
825 Func (arg) # Error! | |
826 Func | |
827 \ (arg) # Error! | |
828 Func | |
829 (arg) # Error! | |
830 Func(arg) # OK | |
831 Func( | |
832 arg) # OK | |
833 Func( | |
834 arg # OK | |
835 ) | |
27537 | 836 < *E1205* |
25700 | 837 White space is not allowed in a `:set` command between the option name and a |
838 following "&", "!", "<", "=", "+=", "-=" or "^=". | |
25402 | 839 |
24569 | 840 |
19181
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841 No curly braces expansion ~ |
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|
842 |
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843 |curly-braces-names| cannot be used. |
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844 |
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|
845 |
27537 | 846 Command modifiers are not ignored ~ |
847 *E1176* | |
848 Using a command modifier for a command that does not use it gives an error. | |
849 | |
850 | |
22936
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851 Dictionary literals ~ |
27321 | 852 *vim9-literal-dict* *E1014* |
22936
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|
853 Traditionally Vim has supported dictionary literals with a {} syntax: > |
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|
854 let dict = {'key': value} |
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|
855 |
23088
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856 Later it became clear that using a simple text key is very common, thus |
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857 literal dictionaries were introduced in a backwards compatible way: > |
22936
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858 let dict = #{key: value} |
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859 |
23088
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860 However, this #{} syntax is unlike any existing language. As it turns out |
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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|
861 that using a literal key is much more common than using an expression, and |
22936
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862 considering that JavaScript uses this syntax, using the {} form for dictionary |
23088
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863 literals is considered a much more useful syntax. In Vim9 script the {} form |
22936
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864 uses literal keys: > |
23666 | 865 var dict = {key: value} |
22936
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866 |
23088
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867 This works for alphanumeric characters, underscore and dash. If you want to |
285cde4b8d0e
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changeset
|
868 use another character, use a single or double quoted string: > |
23666 | 869 var dict = {'key with space': value} |
870 var dict = {"key\twith\ttabs": value} | |
871 var dict = {'': value} # empty key | |
27459 | 872 < *E1139* |
23088
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873 In case the key needs to be an expression, square brackets can be used, just |
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874 like in JavaScript: > |
23666 | 875 var dict = {["key" .. nr]: value} |
22936
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876 |
23827
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patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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877 The key type can be string, number, bool or float. Other types result in an |
28777 | 878 error. Without using [] the value is used as a string, keeping leading zeros. |
879 An expression given with [] is evaluated and then converted to a string. | |
880 Leading zeros will then be dropped: > | |
881 var dict = {000123: 'without', [000456]: 'with'} | |
23827
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
882 echo dict |
28777 | 883 {'456': 'with', '000123': 'without'} |
884 A float only works inside [] because the dot is not accepted otherwise: > | |
885 var dict = {[00.013]: 'float'} | |
886 echo dict | |
887 {'0.013': 'float'} | |
23827
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
888 |
22936
00b0275ffe7f
patch 8.2.2015: Vim9: literal dict #{} is not like any other language
Bram Moolenaar <Bram@vim.org>
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22723
diff
changeset
|
889 |
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
parents:
23974
diff
changeset
|
890 No :xit, :t, :k, :append, :change or :insert ~ |
27459 | 891 *E1100* |
21584
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
Bram Moolenaar <Bram@vim.org>
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21550
diff
changeset
|
892 These commands are too easily confused with local variable names. |
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
Bram Moolenaar <Bram@vim.org>
parents:
21550
diff
changeset
|
893 Instead of `:x` or `:xit` you can use `:exit`. |
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
Bram Moolenaar <Bram@vim.org>
parents:
21550
diff
changeset
|
894 Instead of `:t` you can use `:copy`. |
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
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23974
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|
895 Instead of `:k` you can use `:mark`. |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
896 |
19303 | 897 |
898 Comparators ~ | |
899 | |
900 The 'ignorecase' option is not used for comparators that use strings. | |
27804 | 901 Thus "=~" works like "=~#". |
19181
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|
902 |
94eda51ba9ba
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|
903 |
24569 | 904 Abort after error ~ |
905 | |
906 In legacy script, when an error is encountered, Vim continues to execute | |
907 following lines. This can lead to a long sequence of errors and need to type | |
908 CTRL-C to stop it. In Vim9 script execution of commands stops at the first | |
909 error. Example: > | |
910 vim9script | |
911 var x = does-not-exist | |
912 echo 'not executed' | |
913 | |
914 | |
23666 | 915 For loop ~ |
27537 | 916 *E1254* |
26438 | 917 The loop variable must not be declared yet: > |
26304 | 918 var i = 1 |
919 for i in [1, 2, 3] # Error! | |
920 | |
26438 | 921 It is possible to use a global variable though: > |
922 g:i = 1 | |
923 for g:i in [1, 2, 3] | |
924 echo g:i | |
925 endfor | |
926 | |
23666 | 927 Legacy Vim script has some tricks to make a for loop over a list handle |
928 deleting items at the current or previous item. In Vim9 script it just uses | |
929 the index, if items are deleted then items in the list will be skipped. | |
930 Example legacy script: > | |
931 let l = [1, 2, 3, 4] | |
932 for i in l | |
933 echo i | |
934 call remove(l, index(l, i)) | |
935 endfor | |
936 Would echo: | |
937 1 | |
938 2 | |
939 3 | |
940 4 | |
941 In compiled Vim9 script you get: | |
942 1 | |
943 3 | |
944 Generally, you should not change the list that is iterated over. Make a copy | |
945 first if needed. | |
946 | |
947 | |
19181
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Bram Moolenaar <Bram@vim.org>
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|
948 Conditions and expressions ~ |
27321 | 949 *vim9-boolean* |
22500
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
950 Conditions and expressions are mostly working like they do in other languages. |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
951 Some values are different from legacy Vim script: |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
952 value legacy Vim script Vim9 script ~ |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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changeset
|
953 0 falsy falsy |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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changeset
|
954 1 truthy truthy |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
955 99 truthy Error! |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
956 "0" falsy Error! |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
957 "99" truthy Error! |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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changeset
|
958 "text" falsy Error! |
19181
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|
959 |
22500
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
960 For the "??" operator and when using "!" then there is no error, every value |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
961 is either falsy or truthy. This is mostly like JavaScript, except that an |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
962 empty list and dict is falsy: |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
963 |
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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changeset
|
964 type truthy when ~ |
23466 | 965 bool true, v:true or 1 |
19181
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|
966 number non-zero |
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|
967 float non-zero |
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|
968 string non-empty |
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|
969 blob non-empty |
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|
970 list non-empty (different from JavaScript) |
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|
971 dictionary non-empty (different from JavaScript) |
19968 | 972 func when there is a function name |
23466 | 973 special true or v:true |
19181
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|
974 job when not NULL |
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|
975 channel when not NULL |
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976 class when not NULL |
23466 | 977 object when not NULL (TODO: when isTrue() returns true) |
19181
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|
978 |
22494
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patch 8.2.1795: Vim9: operators && and || have a confusing result
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parents:
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changeset
|
979 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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|
980 one: > |
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patch 8.2.1795: Vim9: operators && and || have a confusing result
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|
981 1 || false == true |
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|
982 0 || 1 == true |
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|
983 0 || false == false |
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changeset
|
984 1 && true == true |
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patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
985 0 && 1 == false |
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patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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|
986 8 || 0 Error! |
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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|
987 'yes' && 0 Error! |
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patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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|
988 [] || 99 Error! |
19181
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|
989 |
22494
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patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
990 When using "!" for inverting, there is no error for using any type and the |
22500
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Bram Moolenaar <Bram@vim.org>
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changeset
|
991 result is a boolean. "!!" can be used to turn any value into boolean: > |
23573 | 992 !'yes' == false |
22500
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parents:
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changeset
|
993 !![] == false |
23573 | 994 !![1, 2, 3] == true |
22494
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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diff
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|
995 |
4c21f7f6f9e3
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Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
996 When using "`.."` for string concatenation arguments of simple types are |
22500
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patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
997 always converted to string: > |
19181
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|
998 'hello ' .. 123 == 'hello 123' |
23466 | 999 'hello ' .. v:true == 'hello true' |
19181
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|
1000 |
26769
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patch 8.2.3913: help for expressions does not mention Vim9 syntax
Bram Moolenaar <Bram@vim.org>
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|
1001 Simple types are Number, Float, Special and Bool. For other types |string()| |
30972227ac8d
patch 8.2.3913: help for expressions does not mention Vim9 syntax
Bram Moolenaar <Bram@vim.org>
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|
1002 should be used. |
27321 | 1003 *false* *true* *null* *E1034* |
28002
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patch 8.2.4526: Vim9: cannot set variables to a null value
Bram Moolenaar <Bram@vim.org>
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changeset
|
1004 In Vim9 script one can use the following predefined values: > |
1012048eed26
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|
1005 true |
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|
1006 false |
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Bram Moolenaar <Bram@vim.org>
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1007 null |
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|
1008 null_blob |
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|
1009 null_channel |
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|
1010 null_dict |
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|
1011 null_function |
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1012 null_job |
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1013 null_list |
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1014 null_partial |
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1015 null_string |
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1016 `true` is the same as `v:true`, `false` the same as `v:false`, `null` the same |
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1017 as `v:null`. |
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1018 |
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|
1019 While `null` has the type "special", the other "null_" types have the type |
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|
1020 indicated by their name. Quite often a null value is handled the same as an |
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1021 empty value, but not always. The values can be useful to clear a script-local |
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|
1022 variable, since they cannot be deleted with `:unlet`. E.g.: > |
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|
1023 var theJob = job_start(...) |
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|
1024 # let the job do its work |
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1025 theJob = null_job |
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1026 |
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1027 The values can also be useful as the default value for an argument: > |
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1028 def MyFunc(b: blob = null_blob) |
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1029 if b == null_blob |
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1030 # b argument was not given |
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1031 |
28141 | 1032 It is possible to compare `null` with any value, this will not give a type |
1033 error. However, comparing `null` with a number, float or bool will always | |
1034 result in `false`. This is different from legacy script, where comparing | |
1035 `null` with zero or `false` would return `true`. | |
1036 | |
28002
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1037 When converting a boolean to a string `false` and `true` are used, not |
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1038 `v:false` and `v:true` like in legacy script. `v:none` has no `none` |
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1039 replacement, it has no equivalent in other languages. |
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1040 |
24128
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1041 Indexing a string with [idx] or taking a slice with [idx : idx] uses character |
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|
1042 indexes instead of byte indexes. Composing characters are included. |
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|
1043 Example: > |
21825 | 1044 echo 'bár'[1] |
1045 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
1046 script this results in the string 'á'. | |
23573 | 1047 A negative index is counting from the end, "[-1]" is the last character. |
23666 | 1048 To exclude the last character use |slice()|. |
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1049 To count composing characters separately use |strcharpart()|. |
23573 | 1050 If the index is out of range then an empty string results. |
1051 | |
1052 In legacy script "++var" and "--var" would be silently accepted and have no | |
1053 effect. This is an error in Vim9 script. | |
1054 | |
1055 Numbers starting with zero are not considered to be octal, only numbers | |
1056 starting with "0o" are octal: "0o744". |scriptversion-4| | |
21825 | 1057 |
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1058 |
21093 | 1059 What to watch out for ~ |
1060 *vim9-gotchas* | |
1061 Vim9 was designed to be closer to often used programming languages, but at the | |
1062 same time tries to support the legacy Vim commands. Some compromises had to | |
1063 be made. Here is a summary of what might be unexpected. | |
1064 | |
1065 Ex command ranges need to be prefixed with a colon. > | |
23666 | 1066 -> legacy Vim: shifts the previous line to the right |
1067 ->func() Vim9: method call in a continuation line | |
1068 :-> Vim9: shifts the previous line to the right | |
21093 | 1069 |
23666 | 1070 %s/a/b legacy Vim: substitute on all lines |
21093 | 1071 x = alongname |
23666 | 1072 % another Vim9: modulo operator in a continuation line |
1073 :%s/a/b Vim9: substitute on all lines | |
1074 't legacy Vim: jump to mark t | |
1075 'text'->func() Vim9: method call | |
1076 :'t Vim9: jump to mark t | |
21093 | 1077 |
21676 | 1078 Some Ex commands can be confused with assignments in Vim9 script: > |
23666 | 1079 g:name = value # assignment |
25939
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1080 :g:pattern:cmd # :global command |
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1081 |
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1082 To avoid confusion between a `:global` or `:substitute` command and an |
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1083 expression or assignment, a few separators cannot be used when these commands |
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1084 are abbreviated to a single character: ':', '-' and '.'. > |
23666 | 1085 g:pattern:cmd # invalid command - ERROR |
25939
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1086 s:pattern:repl # invalid command - ERROR |
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1087 g-pattern-cmd # invalid command - ERROR |
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1088 s-pattern-repl # invalid command - ERROR |
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1089 g.pattern.cmd # invalid command - ERROR |
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1090 s.pattern.repl # invalid command - ERROR |
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1091 |
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1092 Also, there cannot be a space between the command and the separator: > |
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1093 g /pattern/cmd # invalid command - ERROR |
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1094 s /pattern/repl # invalid command - ERROR |
21676 | 1095 |
21093 | 1096 Functions defined with `:def` compile the whole function. Legacy functions |
1097 can bail out, and the following lines are not parsed: > | |
1098 func Maybe() | |
1099 if !has('feature') | |
1100 return | |
1101 endif | |
1102 use-feature | |
1103 endfunc | |
1104 Vim9 functions are compiled as a whole: > | |
1105 def Maybe() | |
1106 if !has('feature') | |
1107 return | |
1108 endif | |
23573 | 1109 use-feature # May give a compilation error |
21093 | 1110 enddef |
1111 For a workaround, split it in two functions: > | |
1112 func Maybe() | |
1113 if has('feature') | |
23666 | 1114 call MaybeInner() |
21093 | 1115 endif |
1116 endfunc | |
1117 if has('feature') | |
1118 def MaybeInner() | |
1119 use-feature | |
1120 enddef | |
1121 endif | |
22171 | 1122 Or put the unsupported code inside an `if` with a constant expression that |
21991 | 1123 evaluates to false: > |
1124 def Maybe() | |
1125 if has('feature') | |
1126 use-feature | |
1127 endif | |
1128 enddef | |
25619 | 1129 The `exists_compiled()` function can also be used for this. |
1130 *vim9-user-command* | |
23666 | 1131 Another side effect of compiling a function is that the presence of a user |
23573 | 1132 command is checked at compile time. If the user command is defined later an |
1133 error will result. This works: > | |
1134 command -nargs=1 MyCommand echom <q-args> | |
1135 def Works() | |
1136 MyCommand 123 | |
1137 enddef | |
1138 This will give an error for "MyCommand" not being defined: > | |
1139 def Works() | |
1140 command -nargs=1 MyCommand echom <q-args> | |
1141 MyCommand 123 | |
1142 enddef | |
1143 A workaround is to invoke the command indirectly with `:execute`: > | |
1144 def Works() | |
1145 command -nargs=1 MyCommand echom <q-args> | |
1146 execute 'MyCommand 123' | |
1147 enddef | |
1148 | |
21991 | 1149 Note that for unrecognized commands there is no check for "|" and a following |
1150 command. This will give an error for missing `endif`: > | |
1151 def Maybe() | |
1152 if has('feature') | use-feature | endif | |
1153 enddef | |
21093 | 1154 |
23305 | 1155 Other differences ~ |
1156 | |
1157 Patterns are used like 'magic' is set, unless explicitly overruled. | |
1158 The 'edcompatible' option value is not used. | |
1159 The 'gdefault' option value is not used. | |
1160 | |
24387 | 1161 You may also find this wiki useful. It was written by an early adopter of |
24103 | 1162 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
23305 | 1163 |
25056 | 1164 *:++* *:--* |
1165 The ++ and -- commands have been added. They are very similar to adding or | |
1166 subtracting one: > | |
1167 ++var | |
1168 var += 1 | |
1169 --var | |
1170 var -= 1 | |
1171 | |
1172 Using ++var or --var in an expression is not supported yet. | |
1173 | |
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1174 ============================================================================== |
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1175 |
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1176 3. New style functions *fast-functions* |
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1177 |
27321 | 1178 *:def* *E1028* |
21825 | 1179 :def[!] {name}([arguments])[: {return-type}] |
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1180 Define a new function by the name {name}. The body of |
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1181 the function follows in the next lines, until the |
27321 | 1182 matching `:enddef`. *E1073* |
1183 *E1011* | |
1184 The {name} must be less than 100 bytes long. | |
1185 *E1003* *E1027* *E1056* *E1059* | |
1186 The type of value used with `:return` must match | |
1187 {return-type}. When {return-type} is omitted or is | |
1188 "void" the function is not expected to return | |
1189 anything. | |
27459 | 1190 *E1077* *E1123* |
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1191 {arguments} is a sequence of zero or more argument |
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1192 declarations. There are three forms: |
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1193 {name}: {type} |
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1194 {name} = {value} |
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1195 {name}: {type} = {value} |
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1196 The first form is a mandatory argument, the caller |
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1197 must always provide them. |
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1198 The second and third form are optional arguments. |
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1199 When the caller omits an argument the {value} is used. |
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1200 |
20856 | 1201 The function will be compiled into instructions when |
21499 | 1202 called, or when `:disassemble` or `:defcompile` is |
1203 used. Syntax and type errors will be produced at that | |
1204 time. | |
20856 | 1205 |
21499 | 1206 It is possible to nest `:def` inside another `:def` or |
1207 `:function` up to about 50 levels deep. | |
27459 | 1208 *E1117* |
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1209 [!] is used as with `:function`. Note that |
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1210 script-local functions cannot be deleted or redefined |
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1211 later in Vim9 script. They can only be removed by |
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1212 reloading the same script. |
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1213 |
27537 | 1214 *:enddef* *E1057* *E1152* *E1173* |
21499 | 1215 :enddef End of a function defined with `:def`. It should be on |
1216 a line by its own. | |
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1217 |
24387 | 1218 You may also find this wiki useful. It was written by an early adopter of |
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1219 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
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1220 |
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1221 If the script the function is defined in is Vim9 script, then script-local |
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1222 variables can be accessed without the "s:" prefix. They must be defined |
20856 | 1223 before the function is compiled. If the script the function is defined in is |
1224 legacy script, then script-local variables must be accessed with the "s:" | |
24387 | 1225 prefix if they do not exist at the time of compiling. |
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1226 |
20552 | 1227 *:defc* *:defcompile* |
1228 :defc[ompile] Compile functions defined in the current script that | |
1229 were not compiled yet. | |
28934
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1230 This will report any errors found during compilation. |
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1231 |
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1232 :defc[ompile] {func} |
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1233 :defc[ompile] debug {func} |
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1234 :defc[ompile] profile {func} |
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1235 Compile function {func}, if needed. Use "debug" and |
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1236 "profile" to specify the compilation mode. |
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1237 This will report any errors found during compilation. |
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1238 |
19404 | 1239 *:disa* *:disassemble* |
1240 :disa[ssemble] {func} Show the instructions generated for {func}. | |
27321 | 1241 This is for debugging and testing. *E1061* |
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1242 Note that for command line completion of {func} you |
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1243 can prepend "s:" to find script-local functions. |
19404 | 1244 |
24911 | 1245 :disa[ssemble] profile {func} |
1246 Like `:disassemble` but with the instructions used for | |
23737 | 1247 profiling. |
1248 | |
24911 | 1249 :disa[ssemble] debug {func} |
1250 Like `:disassemble` but with the instructions used for | |
1251 debugging. | |
1252 | |
21250 | 1253 Limitations ~ |
1254 | |
1255 Local variables will not be visible to string evaluation. For example: > | |
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1256 def MapList(): list<string> |
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1257 var list = ['aa', 'bb', 'cc', 'dd'] |
21250 | 1258 return range(1, 2)->map('list[v:val]') |
1259 enddef | |
1260 | |
1261 The map argument is a string expression, which is evaluated without the | |
1262 function scope. Instead, use a lambda: > | |
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1263 def MapList(): list<string> |
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1264 var list = ['aa', 'bb', 'cc', 'dd'] |
25973 | 1265 return range(1, 2)->map((_, v) => list[v]) |
21250 | 1266 enddef |
1267 | |
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1268 For commands that are not compiled, such as `:edit`, backtick expansion can be |
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1269 used and it can use the local scope. Example: > |
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1270 def Replace() |
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1271 var fname = 'blah.txt' |
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1272 edit `=fname` |
25402 | 1273 enddef |
1274 | |
24278 | 1275 Closures defined in a loop will share the same context. For example: > |
1276 var flist: list<func> | |
25402 | 1277 for i in range(5) |
24278 | 1278 var inloop = i |
1279 flist[i] = () => inloop | |
1280 endfor | |
25402 | 1281 echo range(5)->map((i, _) => flist[i]()) |
1282 # Result: [4, 4, 4, 4, 4] | |
28141 | 1283 < *E1271* |
1284 A closure must be compiled in the context that it is defined in, so that | |
1285 variables in that context can be found. This mostly happens correctly, except | |
1286 when a function is marked for debugging with `breakadd` after it was compiled. | |
28246 | 1287 Make sure to define the breakpoint before compiling the outer function. |
24278 | 1288 |
1289 The "inloop" variable will exist only once, all closures put in the list refer | |
25402 | 1290 to the same instance, which in the end will have the value 4. This is |
1291 efficient, also when looping many times. If you do want a separate context | |
1292 for each closure call a function to define it: > | |
1293 def GetClosure(i: number): func | |
1294 var infunc = i | |
1295 return () => infunc | |
24278 | 1296 enddef |
1297 | |
1298 var flist: list<func> | |
25402 | 1299 for i in range(5) |
1300 flist[i] = GetClosure(i) | |
24278 | 1301 endfor |
25402 | 1302 echo range(5)->map((i, _) => flist[i]()) |
1303 # Result: [0, 1, 2, 3, 4] | |
24278 | 1304 |
27537 | 1305 In some situations, especially when calling a Vim9 closure from legacy |
1306 context, the evaluation will fail. *E1248* | |
1307 | |
1308 | |
1309 Converting a function from legacy to Vim9 ~ | |
1310 *convert_legacy_function_to_vim9* | |
1311 These are the most changes that need to be made to convert a legacy function | |
1312 to a Vim9 function: | |
1313 | |
1314 - Change `func` or `function` to `def`. | |
1315 - Change `endfunc` or `endfunction` to `enddef`. | |
1316 - Add types to the function arguments. | |
1317 - If the function returns something, add the return type. | |
1318 - Change comments to start with # instead of ". | |
1319 | |
1320 For example, a legacy function: > | |
1321 func MyFunc(text) | |
1322 " function body | |
1323 endfunc | |
1324 < Becomes: > | |
1325 def MyFunc(text: string): number | |
1326 # function body | |
1327 enddef | |
1328 | |
1329 - Remove "a:" used for arguments. E.g.: > | |
1330 return len(a:text) | |
1331 < Becomes: > | |
1332 return len(text) | |
1333 | |
1334 - Change `let` used to declare a variable to `var`. | |
1335 - Remove `let` used to assign a value to a variable. This is for local | |
1336 variables already declared and b: w: g: and t: variables. | |
1337 | |
1338 For example, legacy function: > | |
1339 let lnum = 1 | |
1340 let lnum += 3 | |
1341 let b:result = 42 | |
1342 < Becomes: > | |
1343 var lnum = 1 | |
1344 lnum += 3 | |
1345 b:result = 42 | |
1346 | |
1347 - Insert white space in expressions where needed. | |
1348 - Change "." used for concatenation to "..". | |
1349 | |
1350 For example, legacy function: > | |
1351 echo line(1).line(2) | |
1352 < Becomes: > | |
1353 echo line(1) .. line(2) | |
1354 | |
1355 - line continuation does not always require a backslash: > | |
1356 echo ['one', | |
1357 \ 'two', | |
1358 \ 'three' | |
1359 \ ] | |
1360 < Becomes: > | |
1361 echo ['one', | |
1362 'two', | |
1363 'three' | |
1364 ] | |
1365 | |
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1366 ============================================================================== |
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1367 |
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1368 4. Types *vim9-types* |
27321 | 1369 *E1008* *E1009* *E1010* *E1012* |
1370 *E1013* *E1029* *E1030* | |
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1371 The following builtin types are supported: |
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1372 bool |
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1373 number |
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1374 float |
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1375 string |
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1376 blob |
19904
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1377 list<{type}> |
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1378 dict<{type}> |
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1379 job |
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1380 channel |
19646 | 1381 func |
19968 | 1382 func: {type} |
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1383 func({type}, ...) |
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1384 func({type}, ...): {type} |
27321 | 1385 void |
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1386 |
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1387 Not supported yet: |
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1388 tuple<a: {type}, b: {type}, ...> |
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1389 |
25161 | 1390 These types can be used in declarations, but no simple value will actually |
27321 | 1391 have the "void" type. Trying to use a void (e.g. a function without a |
27537 | 1392 return value) results in error *E1031* *E1186* . |
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1393 |
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1394 There is no array type, use list<{type}> instead. For a list constant an |
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1395 efficient implementation is used that avoids allocating lot of small pieces of |
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1396 memory. |
27321 | 1397 *E1005* *E1007* |
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1398 A partial and function can be declared in more or less specific ways: |
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1399 func any kind of function reference, no type |
19968 | 1400 checking for arguments or return value |
25161 | 1401 func: void any number and type of arguments, no return |
1402 value | |
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1403 func: {type} any number and type of arguments with specific |
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1404 return type |
25161 | 1405 |
1406 func() function with no argument, does not return a | |
1407 value | |
1408 func(): void same | |
1409 func(): {type} function with no argument and return type | |
1410 | |
19968 | 1411 func({type}) function with argument type, does not return |
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1412 a value |
19968 | 1413 func({type}): {type} function with argument type and return type |
1414 func(?{type}) function with type of optional argument, does | |
1415 not return a value | |
1416 func(...{type}) function with type of variable number of | |
1417 arguments, does not return a value | |
1418 func({type}, ?{type}, ...{type}): {type} | |
1419 function with: | |
1420 - type of mandatory argument | |
1421 - type of optional argument | |
1422 - type of variable number of arguments | |
1423 - return type | |
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1424 |
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1425 If the return type is "void" the function does not return a value. |
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1426 |
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1427 The reference can also be a |Partial|, in which case it stores extra arguments |
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1428 and/or a dictionary, which are not visible to the caller. Since they are |
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1429 called in the same way the declaration is the same. |
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1430 |
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1431 Custom types can be defined with `:type`: > |
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1432 :type MyList list<string> |
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1433 Custom types must start with a capital letter, to avoid name clashes with |
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1434 builtin types added later, similarly to user functions. |
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1435 {not implemented yet} |
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1436 |
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1437 And classes and interfaces can be used as types: > |
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1438 :class MyClass |
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1439 :var mine: MyClass |
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1440 |
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1441 :interface MyInterface |
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1442 :var mine: MyInterface |
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1443 |
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1444 :class MyTemplate<Targ> |
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1445 :var mine: MyTemplate<number> |
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1446 :var mine: MyTemplate<string> |
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1447 |
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1448 :class MyInterface<Targ> |
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1449 :var mine: MyInterface<number> |
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1450 :var mine: MyInterface<string> |
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1451 {not implemented yet} |
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1452 |
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1453 |
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1454 Variable types and type casting ~ |
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1455 *variable-types* |
21717
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1456 Variables declared in Vim9 script or in a `:def` function have a type, either |
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1457 specified explicitly or inferred from the initialization. |
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1458 |
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1459 Global, buffer, window and tab page variables do not have a specific type, the |
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1460 value can be changed at any time, possibly changing the type. Therefore, in |
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1461 compiled code the "any" type is assumed. |
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1462 |
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1463 This can be a problem when the "any" type is undesired and the actual type is |
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1464 expected to always be the same. For example, when declaring a list: > |
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1465 var l: list<number> = [1, g:two] |
23305 | 1466 At compile time Vim doesn't know the type of "g:two" and the expression type |
1467 becomes list<any>. An instruction is generated to check the list type before | |
1468 doing the assignment, which is a bit inefficient. | |
27459 | 1469 *type-casting* *E1104* |
23305 | 1470 To avoid this, use a type cast: > |
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1471 var l: list<number> = [1, <number>g:two] |
23305 | 1472 The compiled code will then only check that "g:two" is a number and give an |
1473 error if it isn't. This is called type casting. | |
21717
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1474 |
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1475 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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1476 after the "<" or before the ">" (to avoid them being confused with |
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1477 smaller-than and bigger-than operators). |
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1478 |
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1479 The semantics is that, if needed, a runtime type check is performed. The |
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1480 value is not actually changed. If you need to change the type, e.g. to change |
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1481 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
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1482 string to a number. |
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1483 |
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1484 |
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1485 Type inference ~ |
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1486 *type-inference* |
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1487 In general: Whenever the type is clear it can be omitted. For example, when |
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1488 declaring a variable and giving it a value: > |
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1489 var name = 0 # infers number type |
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1490 var name = 'hello' # infers string type |
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1491 |
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1492 The type of a list and dictionary comes from the common type of the values. |
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1493 If the values all have the same type, that type is used for the list or |
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1494 dictionary. If there is a mix of types, the "any" type is used. > |
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1495 [1, 2, 3] list<number> |
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1496 ['a', 'b', 'c'] list<string> |
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1497 [1, 'x', 3] list<any> |
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1498 |
25161 | 1499 The common type of function references, if they do not all have the same |
1500 number of arguments, uses "(...)" to indicate the number of arguments is not | |
1501 specified. For example: > | |
1502 def Foo(x: bool) | |
1503 enddef | |
1504 def Bar(x: bool, y: bool) | |
1505 enddef | |
1506 var funclist = [Foo, Bar] | |
1507 echo funclist->typename() | |
1508 Results in: | |
1509 list<func(...)> | |
1510 | |
24387 | 1511 For script-local variables in Vim9 script the type is checked, also when the |
1512 variable was declared in a legacy function. | |
1513 | |
27623 | 1514 When a type has been declared this is attached to a List or Dictionary. When |
27459 | 1515 later some expression attempts to change the type an error will be given: > |
1516 var ll: list<number> = [1, 2, 3] | |
27492 | 1517 ll->extend(['x']) # Error, 'x' is not a number |
27459 | 1518 |
27623 | 1519 If the type is not declared then it is allowed to change: > |
27492 | 1520 [1, 2, 3]->extend(['x']) # result: [1, 2, 3, 'x'] |
27459 | 1521 |
27623 | 1522 For a variable declaration an inferred type matters: > |
1523 var ll = [1, 2, 3] | |
1524 ll->extend(['x']) # Error, 'x' is not a number | |
1525 That is because the declaration looks like a list of numbers, thus is | |
1526 equivalent to: > | |
1527 var ll: list<number> = [1, 2, 3] | |
1528 If you do want a more permissive list you need to declare the type: > | |
1529 var ll: list<any = [1, 2, 3] | |
1530 ll->extend(['x']) # OK | |
1531 | |
21991 | 1532 |
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1533 Stricter type checking ~ |
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1534 *type-checking* |
21991 | 1535 In legacy Vim script, where a number was expected, a string would be |
1536 automatically converted to a number. This was convenient for an actual number | |
24387 | 1537 such as "123", but leads to unexpected problems (and no error message) if the |
21991 | 1538 string doesn't start with a number. Quite often this leads to hard-to-find |
27804 | 1539 bugs. e.g.: > |
1540 echo 123 == '123' | |
1541 < 1 ~ | |
1542 With an accidental space: > | |
1543 echo 123 == ' 123' | |
1544 < 0 ~ | |
27537 | 1545 *E1206* *E1210* *E1212* |
21991 | 1546 In Vim9 script this has been made stricter. In most places it works just as |
27804 | 1547 before if the value used matches the expected type. There will sometimes be |
22171 | 1548 an error, thus breaking backwards compatibility. For example: |
21991 | 1549 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
25161 | 1550 - Using a string value when setting a number option. |
27459 | 1551 - Using a number where a string is expected. *E1024* *E1105* |
21991 | 1552 |
25973 | 1553 One consequence is that the item type of a list or dict given to |map()| must |
27804 | 1554 not change, if the type was declared. This will give an error in Vim9 |
1555 script: > | |
1556 var mylist: list<number> = [1, 2, 3] | |
1557 echo map(mylist, (i, v) => 'item ' .. i) | |
1558 < E1012: Type mismatch; expected number but got string in map() ~ | |
25161 | 1559 |
27804 | 1560 Instead use |mapnew()|, it creates a new list: > |
1561 var mylist: list<number> = [1, 2, 3] | |
1562 echo mapnew(mylist, (i, v) => 'item ' .. i) | |
1563 < ['item 0', 'item 1', 'item 2'] ~ | |
1564 | |
1565 If the item type was not declared or determined to be "any" it can change to a | |
1566 more specific type. E.g. when a list of mixed types gets changed to a list of | |
1567 strings: > | |
25161 | 1568 var mylist = [1, 2.0, '3'] |
1569 # typename(mylist) == "list<any>" | |
1570 map(mylist, (i, v) => 'item ' .. i) | |
1571 # typename(mylist) == "list<string>", no error | |
27804 | 1572 |
1573 There is a subtle difference between using a list constant directly and | |
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1574 through a variable declaration. Because of type inference, when using a list |
27804 | 1575 constant to initialize a variable, this also sets the declared type: > |
1576 var mylist = [1, 2, 3] | |
1577 # typename(mylist) == "list<number>" | |
1578 echo map(mylist, (i, v) => 'item ' .. i) # Error! | |
1579 | |
1580 When using the list constant directly, the type is not declared and is allowed | |
1581 to change: > | |
1582 echo map([1, 2, 3], (i, v) => 'item ' .. i) # OK | |
1583 | |
1584 The reasoning behind this is that when a type is declared and the list is | |
1585 passed around and changed, the declaration must always hold. So that you can | |
1586 rely on the type to match the declared type. For a constant this is not | |
1587 needed. | |
1588 | |
1589 *E1158* | |
24024 | 1590 Same for |extend()|, use |extendnew()| instead, and for |flatten()|, use |
27804 | 1591 |flattennew()| instead. Since |flatten()| is intended to always change the |
1592 type, it can not be used in Vim9 script. | |
1593 | |
27537 | 1594 *E1211* *E1217* *E1218* *E1219* *E1220* *E1221* |
1595 *E1222* *E1223* *E1224* *E1225* *E1226* *E1227* | |
1596 *E1228* *E1238* *E1250* *E1251* *E1252* *E1253* | |
1597 *E1256* | |
1598 Types are checked for most builtin functions to make it easier to spot | |
1599 mistakes. | |
23573 | 1600 |
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1601 ============================================================================== |
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1602 |
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1603 5. Namespace, Import and Export |
19181
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1604 *vim9script* *vim9-export* *vim9-import* |
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1605 |
27162 | 1606 A Vim9 script can be written to be imported. This means that some items are |
1607 intentionally exported, made available to other scripts. When the exporting | |
1608 script is imported in another script, these exported items can then be used in | |
1609 that script. All the other items remain script-local in the exporting script | |
1610 and cannot be accessed by the importing script. | |
27036 | 1611 |
1612 This mechanism exists for writing a script that can be sourced (imported) by | |
1613 other scripts, while making sure these other scripts only have access to what | |
1614 you want them to. This also avoids using the global namespace, which has a | |
29121 | 1615 risk of name collisions. For example when you have two plugins with similar |
27036 | 1616 functionality. |
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1617 |
27162 | 1618 You can cheat by using the global namespace explicitly. That should be done |
1619 only for things that really are global. | |
21991 | 1620 |
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1621 |
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1622 Namespace ~ |
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1623 *vim9-namespace* |
19303 | 1624 To recognize a file that can be imported the `vim9script` statement must |
23974
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1625 appear as the first statement in the file (see |vim9-mix| for an exception). |
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1626 It tells Vim to interpret the script in its own namespace, instead of the |
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1627 global namespace. If a file starts with: > |
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1628 vim9script |
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1629 var myvar = 'yes' |
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1630 Then "myvar" will only exist in this file. While without `vim9script` it would |
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1631 be available as `g:myvar` from any other script and function. |
27459 | 1632 *E1101* |
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1633 The variables at the file level are very much like the script-local "s:" |
20115 | 1634 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
1635 deleted. | |
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1636 |
20115 | 1637 In Vim9 script the global "g:" namespace can still be used as before. And the |
1638 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
1639 declared and they can be deleted. | |
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1640 |
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1641 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
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1642 Vim default value, like with: > |
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1643 :set cpo&vim |
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1644 One of the effects is that |line-continuation| is always enabled. |
24150
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1645 The original value of 'cpoptions' is restored at the end of the script, while |
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1646 flags added or removed in the script are also added to or removed from the |
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1647 original value to get the same effect. The order of flags may change. |
26745
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1648 In the |vimrc| file sourced on startup this does not happen. |
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1649 |
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1650 *vim9-mix* |
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1651 There is one way to use both legacy and Vim9 syntax in one script file: > |
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1652 " comments may go here |
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1653 if !has('vim9script') |
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1654 " legacy script commands go here |
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1655 finish |
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1656 endif |
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1657 vim9script |
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1658 # Vim9 script commands go here |
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1659 This allows for writing a script that takes advantage of the Vim9 script |
24024 | 1660 syntax if possible, but will also work on a Vim version without it. |
23974
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1661 |
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1662 This can only work in two ways: |
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1663 1. The "if" statement evaluates to false, the commands up to `endif` are |
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1664 skipped and `vim9script` is then the first command actually executed. |
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1665 2. The "if" statement evaluates to true, the commands up to `endif` are |
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1666 executed and `finish` bails out before reaching `vim9script`. |
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1667 |
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1668 |
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1669 Export ~ |
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1670 *:export* *:exp* |
21499 | 1671 Exporting an item can be written as: > |
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1672 export const EXPORTED_CONST = 1234 |
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1673 export var someValue = ... |
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1674 export final someValue = ... |
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1675 export const someValue = ... |
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1676 export def MyFunc() ... |
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1677 export class MyClass ... |
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1678 export interface MyClass ... |
27321 | 1679 < *E1043* *E1044* |
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1680 As this suggests, only constants, variables, `:def` functions and classes can |
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1681 be exported. {not implemented yet: class, interface} |
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1682 |
20856 | 1683 *E1042* |
1684 `:export` can only be used in Vim9 script, at the script level. | |
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1685 |
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1686 |
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1687 Import ~ |
27537 | 1688 *:import* *:imp* *E1094* *E1047* *E1262* |
1689 *E1048* *E1049* *E1053* *E1071* *E1236* | |
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1690 The exported items can be imported in another Vim9 script: > |
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1691 import "myscript.vim" |
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1692 |
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1693 This makes each item available as "myscript.item". |
27537 | 1694 *:import-as* *E1257* *E1261* |
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1695 In case the name is long or ambiguous, another name can be specified: > |
27036 | 1696 import "thatscript.vim" as that |
27537 | 1697 < *E1060* *E1258* *E1259* *E1260* |
27036 | 1698 Then you can use "that.EXPORTED_CONST", "that.someValue", etc. You are free |
1699 to choose the name "that". Use something that will be recognized as referring | |
27459 | 1700 to the imported script. Avoid command names, command modifiers and builtin |
1701 function names, because the name will shadow them. | |
1702 If the name starts with a capital letter it can also shadow global user | |
1703 commands and functions. Also, you cannot use the name for something else in | |
1704 the script, such as a function or variable name. | |
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1705 |
27036 | 1706 In case the dot in the name is undesired, a local reference can be made for a |
1707 function: > | |
1708 var LongFunc = that.LongFuncName | |
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1709 |
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1710 This also works for constants: > |
27036 | 1711 const MAXLEN = that.MAX_LEN_OF_NAME |
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1712 |
27036 | 1713 This does not work for variables, since the value would be copied once and |
1714 when changing the variable the copy will change, not the original variable. | |
1715 You will need to use the full name, with the dot. | |
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1716 |
27321 | 1717 The full syntax of the command is: |
1718 import {filename} [as {name}] | |
1719 Where {filename} is an expression that must evaluate to a string. Without the | |
1720 "as {name}" part it must end in ".vim". {name} must consist of letters, | |
1721 digits and '_', like |internal-variables|. | |
1722 | |
22171 | 1723 `:import` can also be used in legacy Vim script. The imported items still |
1724 become script-local, even when the "s:" prefix is not given. | |
1725 | |
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1726 `:import` can not be used in a function. Imported items are intended to exist |
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1727 at the script level and only imported once. |
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1728 |
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1729 The script name after `import` can be: |
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1730 - A relative path, starting "." or "..". This finds a file relative to the |
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1731 location of the script file itself. This is useful to split up a large |
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1732 plugin into several files. |
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1733 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
22723 | 1734 will rarely be used. |
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1735 - A path not being relative or absolute. This will be found in the |
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1736 "import" subdirectories of 'runtimepath' entries. The name will usually be |
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1737 longer and unique, to avoid loading the wrong file. |
25619 | 1738 Note that "after/import" is not used. |
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1739 |
27036 | 1740 If the name does not end in ".vim" then the use of "as name" is required. |
1741 | |
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1742 Once a vim9 script file has been imported, the result is cached and used the |
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1743 next time the same script is imported. It will not be read again. |
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1744 |
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1745 It is not allowed to import the same script twice, also when using two |
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1746 different "as" names. |
27036 | 1747 |
1748 When using the imported name the dot and the item name must be in the same | |
1749 line, there can be no line break: > | |
1750 echo that. | |
1751 name # Error! | |
1752 echo that | |
1753 .name # Error! | |
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1754 |
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1755 To refer to a function in an imported script in a mapping, |<SID>| can be |
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1756 used: > |
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1757 noremap <silent> ,a :call <SID>name.Function()<CR> |
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1758 |
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1759 When the mapping is defined "<SID>name." will be replaced with <SNR> and the |
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1760 script ID of the imported script. |
29121 | 1761 An even simpler solution is using |<ScriptCmd>|: > |
1762 noremap ,a <ScriptCmd>name.Function()<CR> | |
1763 < | |
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1764 *:import-cycle* |
27537 | 1765 The `import` commands are executed when encountered. If script A imports |
1766 script B, and B (directly or indirectly) imports A, this will be skipped over. | |
1767 At this point items in A after "import B" will not have been processed and | |
1768 defined yet. Therefore cyclic imports can exist and not result in an error | |
1769 directly, but may result in an error for items in A after "import B" not being | |
1770 defined. This does not apply to autoload imports, see the next section. | |
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1771 |
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1772 |
27162 | 1773 Importing an autoload script ~ |
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1774 *vim9-autoload* |
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1775 For optimal startup speed, loading scripts should be postponed until they are |
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1776 actually needed. Using the autoload mechanism is recommended: |
27537 | 1777 *E1264* |
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1778 1. In the plugin define user commands, functions and/or mappings that refer to |
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1779 items imported from an autoload script. > |
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1780 import autoload 'for/search.vim' |
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1781 command -nargs=1 SearchForStuff search.Stuff(<f-args>) |
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1782 |
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1783 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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1784 The "SearchForStuff" command is now available to the user. |
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1785 |
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1786 The "autoload" argument to `:import` means that the script is not loaded |
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1787 until one of the items is actually used. The script will be found under |
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1788 the "autoload" directory in 'runtimepath' instead of the "import" |
28379 | 1789 directory. Alternatively a relative or absolute name can be used, see |
1790 below. | |
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1791 |
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1792 2. In the autoload script put the bulk of the code. > |
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1793 vim9script |
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1794 export def Stuff(arg: string) |
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1795 ... |
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1796 |
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1797 < This goes in .../autoload/for/search.vim. |
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1798 |
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1799 Putting the "search.vim" script under the "/autoload/for/" directory has |
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1800 the effect that "for#search#" will be prefixed to every exported item. The |
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1801 prefix is obtained from the file name, as you would to manually in a |
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1802 legacy autoload script. Thus the exported function can be found with |
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1803 "for#search#Stuff", but you would normally use `import autoload` and not |
28141 | 1804 use the prefix (which has the side effect of loading the autoload script |
1805 when compiling a function that encounters this name). | |
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1806 |
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1807 You can split up the functionality and import other scripts from the |
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1808 autoload script as you like. This way you can share code between plugins. |
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1809 |
28379 | 1810 Searching for the autoload script in all entries in 'runtimepath' can be a bit |
1811 slow. If the plugin knows where the script is located, quite often a relative | |
1812 path can be used. This avoids the search and should be quite a bit faster. | |
1813 Another advantage is that the script name does not need to be unique. An | |
1814 absolute path is also possible. Examples: > | |
1815 import autoload '../lib/implement.vim' | |
1816 import autoload MyScriptsDir .. '/lib/implement.vim' | |
1817 | |
27162 | 1818 For defining a mapping that uses the imported autoload script the special key |
1819 |<ScriptCmd>| is useful. It allows for a command in a mapping to use the | |
1820 script context of where the mapping was defined. | |
1821 | |
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1822 When compiling a `:def` function and a function in an autoload script is |
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1823 encountered, the script is not loaded until the `:def` function is called. |
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1824 This also means you get any errors only at runtime, since the argument and |
28141 | 1825 return types are not known yet. If you would use the name with '#' characters |
1826 then the autoload script IS loaded. | |
1827 | |
1828 Be careful to not refer to an item in an autoload script that does trigger | |
1829 loading it unintentionally. For example, when setting an option that takes a | |
1830 function name, make sure to use a string, not a function reference: > | |
1831 import autoload 'qftf.vim' | |
1832 &quickfixtextfunc = 'qftf.Func' # autoload script NOT loaded | |
1833 &quickfixtextfunc = qftf.Func # autoload script IS loaded | |
1834 On the other hand, it can be useful to load the script early, at a time when | |
1835 any errors should be given. | |
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1836 |
27162 | 1837 For testing the |test_override()| function can be used to have the |
1838 `import autoload` load the script right away, so that the items and types can | |
1839 be checked without waiting for them to be actually used: > | |
1840 test_override('autoload', 1) | |
1841 Reset it later with: > | |
1842 test_override('autoload', 0) | |
1843 Or: > | |
1844 test_override('ALL', 0) | |
1845 | |
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1846 |
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1847 Import in legacy Vim script ~ |
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1848 |
20856 | 1849 If an `import` statement is used in legacy Vim script, the script-local "s:" |
27162 | 1850 namespace will be used for the imported items, even when "s:" is not |
1851 specified. | |
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1852 |
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1853 |
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1854 ============================================================================== |
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1855 |
22328 | 1856 6. Future work: classes *vim9-classes* |
1857 | |
1858 Above "class" was mentioned a few times, but it has not been implemented yet. | |
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1859 Most of Vim9 script can be created without this functionality, and since |
22328 | 1860 implementing classes is going to be a lot of work, it is left for the future. |
1861 For now we'll just make sure classes can be added later. | |
1862 | |
1863 Thoughts: | |
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1864 - `class` / `endclass`, the whole class must be in one file |
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1865 - Class names are always CamelCase (to avoid a name clash with builtin types) |
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1866 - A single constructor called "constructor" |
22328 | 1867 - Single inheritance with `class ThisClass extends BaseClass` |
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1868 - `abstract class` (class with incomplete implementation) |
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1869 - `interface` / `endinterface` (abstract class without any implementation) |
22328 | 1870 - `class SomeClass implements SomeInterface` |
1871 - Generics for class: `class <Tkey, Tentry>` | |
1872 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
1873 | |
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1874 Again, much of this is from TypeScript with a slightly different syntax. |
22328 | 1875 |
1876 Some things that look like good additions: | |
1877 - Use a class as an interface (like Dart) | |
1878 - Extend a class with methods, using an import (like Dart) | |
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1879 - Mixins |
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1880 - For testing: Mock mechanism |
22328 | 1881 |
1882 An important class that will be provided is "Promise". Since Vim is single | |
1883 threaded, connecting asynchronous operations is a natural way of allowing | |
1884 plugins to do their work without blocking the user. It's a uniform way to | |
1885 invoke callbacks and handle timeouts and errors. | |
1886 | |
28010 | 1887 Some commands have already been reserved: |
1888 *:class* | |
1889 *:endclass* | |
1890 *:abstract* | |
1891 *:enum* | |
1892 *:endenum* | |
1893 *:interface* | |
1894 *:endinterface* | |
1895 *:static* | |
1896 *:type* | |
1897 | |
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1898 Some examples: > |
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1899 |
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1900 abstract class Person |
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1901 static const prefix = 'xxx' |
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1902 var name: string |
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1903 |
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1904 def constructor(name: string) |
25402 | 1905 this.name = name |
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1906 enddef |
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1907 |
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1908 def display(): void |
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1909 echo name |
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1910 enddef |
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1911 |
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1912 abstract def find(string): Person |
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1913 endclass |
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1914 |
22328 | 1915 ============================================================================== |
1916 | |
19181
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1917 9. Rationale *vim9-rationale* |
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1918 |
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1919 The :def command ~ |
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1920 |
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1921 Plugin writers have asked for much faster Vim script. Investigations have |
19303 | 1922 shown that keeping the existing semantics of function calls make this close to |
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1923 impossible, because of the overhead involved with calling a function, setting |
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1924 up the local function scope and executing lines. There are many details that |
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1925 need to be handled, such as error messages and exceptions. The need to create |
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1926 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1927 much overhead that cannot be avoided. |
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1928 |
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1929 Therefore the `:def` method to define a new-style function had to be added, |
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1930 which allows for a function with different semantics. Most things still work |
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1931 as before, but some parts do not. A new way to define a function was |
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1932 considered the best way to separate the legacy style code from Vim9 style code. |
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1933 |
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1934 Using "def" to define a function comes from Python. Other languages use |
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1935 "function" which clashes with legacy Vim script. |
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1936 |
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1937 |
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1938 Type checking ~ |
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1939 |
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1940 When compiling lines of Vim commands into instructions as much as possible |
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1941 should be done at compile time. Postponing it to runtime makes the execution |
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1942 slower and means mistakes are found only later. For example, when |
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1943 encountering the "+" character and compiling this into a generic add |
23666 | 1944 instruction, at runtime the instruction would have to inspect the type of the |
1945 arguments and decide what kind of addition to do. And when the type is | |
1946 dictionary throw an error. If the types are known to be numbers then an "add | |
1947 number" instruction can be used, which is faster. The error can be given at | |
1948 compile time, no error handling is needed at runtime, since adding two numbers | |
1949 cannot fail. | |
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1950 |
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1951 The syntax for types, using <type> for compound types, is similar to Java. It |
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1952 is easy to understand and widely used. The type names are what were used in |
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1953 Vim before, with some additions such as "void" and "bool". |
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1954 |
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1955 |
22328 | 1956 Removing clutter and weirdness ~ |
20856 | 1957 |
22328 | 1958 Once decided that `:def` functions have different syntax than legacy functions, |
1959 we are free to add improvements to make the code more familiar for users who | |
1960 know popular programming languages. In other words: remove weird things that | |
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1961 only Vim does. |
22328 | 1962 |
1963 We can also remove clutter, mainly things that were done to make Vim script | |
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1964 backwards compatible with the good old Vi commands. |
20856 | 1965 |
22328 | 1966 Examples: |
29104 | 1967 - Drop `:call` for calling a function and `:eval` for evaluating an |
1968 expression. | |
22328 | 1969 - Drop using a leading backslash for line continuation, automatically figure |
1970 out where an expression ends. | |
20856 | 1971 |
22328 | 1972 However, this does require that some things need to change: |
1973 - Comments start with # instead of ", to avoid confusing them with strings. | |
29104 | 1974 This is good anyway, it is also used by several popular languages. |
22328 | 1975 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
1976 expressions (single quote can be a string or a mark, "/" can be divide or a | |
1977 search command, etc.). | |
1978 | |
1979 Goal is to limit the differences. A good criteria is that when the old syntax | |
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1980 is accidentally used you are very likely to get an error message. |
20856 | 1981 |
1982 | |
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1983 Syntax and semantics from popular languages ~ |
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1984 |
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1985 Script writers have complained that the Vim script syntax is unexpectedly |
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1986 different from what they are used to. To reduce this complaint popular |
20856 | 1987 languages are used as an example. At the same time, we do not want to abandon |
1988 the well-known parts of legacy Vim script. | |
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1989 |
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1990 For many things TypeScript is followed. It's a recent language that is |
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1991 gaining popularity and has similarities with Vim script. It also has a |
22328 | 1992 mix of static typing (a variable always has a known value type) and dynamic |
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1993 typing (a variable can have different types, this changes at runtime). Since |
22328 | 1994 legacy Vim script is dynamically typed and a lot of existing functionality |
1995 (esp. builtin functions) depends on that, while static typing allows for much | |
1996 faster execution, we need to have this mix in Vim9 script. | |
1997 | |
22171 | 1998 There is no intention to completely match TypeScript syntax and semantics. We |
1999 just want to take those parts that we can use for Vim and we expect Vim users | |
22328 | 2000 will be happy with. TypeScript is a complex language with its own history, |
2001 advantages and disadvantages. To get an idea of the disadvantages read the | |
2002 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
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2003 parts" and read the "Things to avoid" section. |
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2004 |
22328 | 2005 People familiar with other languages (Java, Python, etc.) will also find |
2006 things in TypeScript that they do not like or do not understand. We'll try to | |
2007 avoid those things. | |
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2008 |
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2009 Specific items from TypeScript we avoid: |
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2010 - Overloading "+", using it both for addition and string concatenation. This |
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2011 goes against legacy Vim script and often leads to mistakes. For that reason |
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2012 we will keep using ".." for string concatenation. Lua also uses ".." this |
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2013 way. And it allows for conversion to string for more values. |
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2014 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
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2015 cannot assign the value to a boolean. That is inconsistent and can be |
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2016 annoying. Vim recognizes an expression with && or || and allows using the |
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2017 result as a bool. The |falsy-operator| was added for the mechanism to use a |
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2018 default value. |
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2019 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
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2020 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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2021 Falsy. |
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2022 - TypeScript has various "Readonly" types, which have limited usefulness, |
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2023 since a type cast can remove the immutable nature. Vim locks the value, |
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2024 which is more flexible, but is only checked at runtime. |
27459 | 2025 - TypeScript has a complicated "import" statement that does not match how the |
2026 Vim import mechanism works. A much simpler mechanism is used instead, which | |
2027 matches that the imported script is only sourced once. | |
22171 | 2028 |
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2029 |
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2030 Declarations ~ |
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2031 |
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2032 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
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2033 are used. That is different, thus it's good to use a different command: |
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2034 `:var`. This is used in many languages. The semantics might be slightly |
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2035 different, but it's easily recognized as a declaration. |
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2036 |
23047 | 2037 Using `:const` for constants is common, but the semantics varies. Some |
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2038 languages only make the variable immutable, others also make the value |
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2039 immutable. Since "final" is well known from Java for only making the variable |
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2040 immutable we decided to use that. And then `:const` can be used for making |
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2041 both immutable. This was also used in legacy Vim script and the meaning is |
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2042 almost the same. |
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2043 |
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2044 What we end up with is very similar to Dart: > |
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2045 :var name # mutable variable and value |
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2046 :final name # immutable variable, mutable value |
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2047 :const name # immutable variable and value |
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2048 |
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2049 Since legacy and Vim9 script will be mixed and global variables will be |
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2050 shared, optional type checking is desirable. Also, type inference will avoid |
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2051 the need for specifying the type in many cases. The TypeScript syntax fits |
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2052 best for adding types to declarations: > |
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2053 var name: string # string type is specified |
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2054 ... |
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2055 name = 'John' |
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2056 const greeting = 'hello' # string type is inferred |
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2057 |
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2058 This is how we put types in a declaration: > |
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2059 var mylist: list<string> |
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2060 final mylist: list<string> = ['foo'] |
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2061 def Func(arg1: number, arg2: string): bool |
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2062 |
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2063 Two alternatives were considered: |
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2064 1. Put the type before the name, like Dart: > |
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2065 var list<string> mylist |
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2066 final list<string> mylist = ['foo'] |
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2067 def Func(number arg1, string arg2) bool |
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2068 2. Put the type after the variable name, but do not use a colon, like Go: > |
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2069 var mylist list<string> |
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2070 final mylist list<string> = ['foo'] |
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2071 def Func(arg1 number, arg2 string) bool |
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2072 |
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2073 The first is more familiar for anyone used to C or Java. The second one |
22565 | 2074 doesn't really have an advantage over the first, so let's discard the second. |
22391
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2075 |
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2076 Since we use type inference the type can be left out when it can be inferred |
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2077 from the value. This means that after `var` we don't know if a type or a name |
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2078 follows. That makes parsing harder, not only for Vim but also for humans. |
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2079 Also, it will not be allowed to use a variable name that could be a type name, |
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2080 using `var string string` is too confusing. |
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2081 |
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2082 The chosen syntax, using a colon to separate the name from the type, adds |
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2083 punctuation, but it actually makes it easier to recognize the parts of a |
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2084 declaration. |
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2085 |
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2086 |
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2087 Expressions ~ |
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2088 |
22565 | 2089 Expression evaluation was already close to what other languages are doing. |
2090 Some details are unexpected and can be improved. For example a boolean | |
2091 condition would accept a string, convert it to a number and check if the | |
2092 number is non-zero. This is unexpected and often leads to mistakes, since | |
2093 text not starting with a number would be converted to zero, which is | |
22723 | 2094 considered false. Thus using a string for a condition would often not give an |
2095 error and be considered false. That is confusing. | |
22391
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2096 |
23047 | 2097 In Vim9 type checking is stricter to avoid mistakes. Where a condition is |
22565 | 2098 used, e.g. with the `:if` command and the `||` operator, only boolean-like |
2099 values are accepted: | |
2100 true: `true`, `v:true`, `1`, `0 < 9` | |
2101 false: `false`, `v:false`, `0`, `0 > 9` | |
2102 Note that the number zero is false and the number one is true. This is more | |
22723 | 2103 permissive than most other languages. It was done because many builtin |
29104 | 2104 functions return these values, and changing that causes more problems than it |
2105 solves. After using this for a while it turned out to work well. | |
22391
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2106 |
22565 | 2107 If you have any type of value and want to use it as a boolean, use the `!!` |
2108 operator: | |
29104 | 2109 true: `!!'text'` `!![99]` `!!{'x': 1}` `!!99` |
2110 false: `!!''` `!![]` `!!{}` | |
22565 | 2111 |
2112 From a language like JavaScript we have this handy construct: > | |
2113 GetName() || 'unknown' | |
2114 However, this conflicts with only allowing a boolean for a condition. | |
2115 Therefore the "??" operator was added: > | |
2116 GetName() ?? 'unknown' | |
2117 Here you can explicitly express your intention to use the value as-is and not | |
2118 result in a boolean. This is called the |falsy-operator|. | |
22391
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2119 |
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2120 |
19181
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2121 Import and Export ~ |
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2122 |
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2123 A problem of legacy Vim script is that by default all functions and variables |
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2124 are global. It is possible to make them script-local, but then they are not |
22171 | 2125 available in other scripts. This defies the concept of a package that only |
2126 exports selected items and keeps the rest local. | |
19181
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2127 |
21825 | 2128 In Vim9 script a mechanism very similar to the JavaScript import and export |
19181
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2129 mechanism is supported. It is a variant to the existing `:source` command |
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2130 that works like one would expect: |
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2131 - Instead of making everything global by default, everything is script-local, |
29104 | 2132 some of these are exported. |
22171 | 2133 - When importing a script the symbols that are imported are explicitly listed, |
2134 avoiding name conflicts and failures if functionality is added later. | |
19181
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2135 - The mechanism allows for writing a big, long script with a very clear API: |
29104 | 2136 the exported functions, variables and classes. |
19181
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2137 - By using relative paths loading can be much faster for an import inside of a |
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2138 package, no need to search many directories. |
29104 | 2139 - Once an import has been used, its items are cached and loading it again is |
2140 not needed. | |
19181
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2141 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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2142 |
29104 | 2143 When sourcing a Vim9 script (from a Vim9 or legacy script), only the items |
2144 defined globally can be used, not the exported items. Alternatives | |
2145 considered: | |
20856 | 2146 - All the exported items become available as script-local items. This makes |
22171 | 2147 it uncontrollable what items get defined and likely soon leads to trouble. |
20856 | 2148 - Use the exported items and make them global. Disadvantage is that it's then |
2149 not possible to avoid name clashes in the global namespace. | |
2150 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
2151 makes it difficult to use scripts for testing, or sourcing them from the | |
2152 command line to try them out. | |
29104 | 2153 Note that you CAN also use `:import` in legacy Vim script, see above. |
20856 | 2154 |
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2155 |
22328 | 2156 Compiling functions early ~ |
2157 | |
2158 Functions are compiled when called or when `:defcompile` is used. Why not | |
2159 compile them early, so that syntax and type errors are reported early? | |
2160 | |
2161 The functions can't be compiled right away when encountered, because there may | |
2162 be forward references to functions defined later. Consider defining functions | |
2163 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
2164 to reorder the functions to avoid forward references. | |
2165 | |
2166 An alternative would be to first scan through the file to locate items and | |
2167 figure out their type, so that forward references are found, and only then | |
2168 execute the script and compile the functions. This means the script has to be | |
2169 parsed twice, which is slower, and some conditions at the script level, such | |
2170 as checking if a feature is supported, are hard to use. An attempt was made | |
29104 | 2171 to see if it works, but it turned out to be impossible to make work well. |
22328 | 2172 |
2173 It would be possible to compile all the functions at the end of the script. | |
2174 The drawback is that if a function never gets called, the overhead of | |
2175 compiling it counts anyway. Since startup speed is very important, in most | |
2176 cases it's better to do it later and accept that syntax and type errors are | |
2177 only reported then. In case these errors should be found early, e.g. when | |
29104 | 2178 testing, a `:defcompile` command at the end of the script will help out. |
22328 | 2179 |
2180 | |
29104 | 2181 Why not use an existing embedded language? ~ |
19181
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2182 |
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2183 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
22328 | 2184 these interfaces have never become widely used, for various reasons. When |
2185 Vim9 was designed a decision was made to make these interfaces lower priority | |
2186 and concentrate on Vim script. | |
19181
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2187 |
22328 | 2188 Still, plugin writers may find other languages more familiar, want to use |
2189 existing libraries or see a performance benefit. We encourage plugin authors | |
29104 | 2190 to write code in any language and run it as an external process, using jobs |
2191 and channels. We can try to make this easier somehow. | |
22328 | 2192 |
2193 Using an external tool also has disadvantages. An alternative is to convert | |
19181
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2194 the tool into Vim script. For that to be possible without too much |
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2195 translation, and keeping the code fast at the same time, the constructs of the |
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2196 tool need to be supported. Since most languages support classes the lack of |
22171 | 2197 support for classes in Vim is then a problem. |
19181
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2198 |
22328 | 2199 |
2200 Classes ~ | |
2201 | |
2202 Vim supports a kind-of object oriented programming by adding methods to a | |
2203 dictionary. With some care this can be made to work, but it does not look | |
2204 like real classes. On top of that, it's quite slow, because of the use of | |
2205 dictionaries. | |
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2206 |
29121 | 2207 It would be good to support real classes, and this is planned for a later |
29104 | 2208 version. The support is a "minimal common functionality" of class support in |
2209 most languages. It will work much like Java, which is the most popular | |
2210 programming language. | |
19181
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2211 |
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2212 |
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2213 |
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2214 vim:tw=78:ts=8:noet:ft=help:norl: |