Mercurial > vim
annotate runtime/doc/vim9.txt @ 25773:11b656e74444
Update runtime files
Commit: https://github.com/vim/vim/commit/6c391a74fe90190796ca0b0c010112948a6e75d7
Author: Bram Moolenaar <Bram@vim.org>
Date: Thu Sep 9 21:55:11 2021 +0200
Update runtime files
author | Bram Moolenaar <Bram@vim.org> |
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date | Thu, 09 Sep 2021 22:00:10 +0200 |
parents | d4faa2c5211b |
children | 65de67669df3 |
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25773 | 1 *vim9.txt* For Vim version 8.2. Last change: 2021 Sep 08 |
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4 VIM REFERENCE MANUAL by Bram Moolenaar |
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7 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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8 |
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9 Vim9 script commands and expressions. *Vim9* *vim9* |
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10 |
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11 Most expression help is in |eval.txt|. This file is about the new syntax and |
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12 features in Vim9 script. |
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13 |
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14 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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23466 | 17 1. What is Vim9 script? |Vim9-script| |
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18 2. Differences |vim9-differences| |
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19 3. New style functions |fast-functions| |
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20 4. Types |vim9-types| |
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21 5. Namespace, Import and Export |vim9script| |
22328 | 22 6. Future work: classes |vim9-classes| |
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23 |
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24 9. Rationale |vim9-rationale| |
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25 |
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26 ============================================================================== |
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27 |
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28 1. What is Vim9 script? *Vim9-script* |
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29 |
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30 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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31 |
20241 | 32 Vim script has been growing over time, while preserving backwards |
33 compatibility. That means bad choices from the past often can't be changed | |
20965 | 34 and compatibility with Vi restricts possible solutions. Execution is quite |
20241 | 35 slow, each line is parsed every time it is executed. |
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36 |
20241 | 37 The main goal of Vim9 script is to drastically improve performance. This is |
38 accomplished by compiling commands into instructions that can be efficiently | |
39 executed. An increase in execution speed of 10 to 100 times can be expected. | |
40 | |
41 A secondary goal is to avoid Vim-specific constructs and get closer to | |
42 commonly used programming languages, such as JavaScript, TypeScript and Java. | |
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43 |
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44 The performance improvements can only be achieved by not being 100% backwards |
20552 | 45 compatible. For example, making function arguments available in the |
46 "a:" dictionary adds quite a lot of overhead. In a Vim9 function this | |
47 dictionary is not available. Other differences are more subtle, such as how | |
48 errors are handled. | |
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49 |
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50 The Vim9 script syntax and semantics are used in: |
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51 - a function defined with the `:def` command |
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52 - a script file where the first command is `vim9script` |
22328 | 53 - an autocommand defined in the context of the above |
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54 - a command prefixed with the `vim9cmd` command modifier |
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23573 | 56 When using `:function` in a Vim9 script file the legacy syntax is used, with |
57 the highest |scriptversion|. However, this can be confusing and is therefore | |
58 discouraged. | |
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59 |
20241 | 60 Vim9 script and legacy Vim script can be mixed. There is no requirement to |
22328 | 61 rewrite old scripts, they keep working as before. You may want to use a few |
62 `:def` functions for code that needs to be fast. | |
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63 |
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64 :vim9[cmd] {cmd} *:vim9* *:vim9cmd* |
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65 Execute {cmd} using Vim9 script syntax and semantics. |
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66 Useful when typing a command and in a legacy script or |
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67 function. |
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68 |
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69 :leg[acy] {cmd} *:leg* *:legacy* |
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70 Execute {cmd} using legacy script syntax and semantics. Only |
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71 useful in a Vim9 script or a :def function. |
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72 Note that {cmd} cannot use local variables, since it is parsed |
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73 with legacy expression syntax. |
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74 |
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75 ============================================================================== |
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76 |
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77 2. Differences from legacy Vim script *vim9-differences* |
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78 |
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79 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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80 |
22441 | 81 Overview ~ |
82 | |
83 Brief summary of the differences you will most often encounter when using Vim9 | |
84 script and `:def` functions; details are below: | |
85 - Comments start with #, not ": > | |
23573 | 86 echo "hello" # comment |
22441 | 87 - Using a backslash for line continuation is hardly ever needed: > |
23573 | 88 echo "hello " |
22441 | 89 .. yourName |
90 .. ", how are you?" | |
91 - White space is required in many places. | |
92 - Assign values without `:let`, declare variables with `:var`: > | |
23573 | 93 var count = 0 |
22441 | 94 count += 3 |
95 - Constants can be declared with `:final` and `:const`: > | |
23573 | 96 final matches = [] # add matches |
22441 | 97 const names = ['Betty', 'Peter'] # cannot be changed |
98 - `:final` cannot be used as an abbreviation of `:finally`. | |
99 - Variables and functions are script-local by default. | |
100 - Functions are declared with argument types and return type: > | |
101 def CallMe(count: number, message: string): bool | |
102 - Call functions without `:call`: > | |
23573 | 103 writefile(['done'], 'file.txt') |
24751 | 104 - You cannot use `:xit`, `:t`, `:k`, `:append`, `:change`, `:insert`, `:open`, |
105 and `:s` or `:d` with only flags. | |
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106 or curly-braces names. |
22441 | 107 - A range before a command must be prefixed with a colon: > |
23573 | 108 :%s/this/that |
25700 | 109 - Executing a register with "@r" does not work, you can prepend a colon or use |
110 `:exe`: > | |
111 :exe @a | |
23573 | 112 - Unless mentioned specifically, the highest |scriptversion| is used. |
22441 | 113 |
114 | |
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115 Comments starting with # ~ |
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116 |
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117 In legacy Vim script comments start with double quote. In Vim9 script |
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118 comments start with #. > |
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119 # declarations |
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120 var count = 0 # number of occurrences |
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121 |
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122 The reason is that a double quote can also be the start of a string. In many |
21825 | 123 places, especially halfway through an expression with a line break, it's hard |
124 to tell what the meaning is, since both a string and a comment can be followed | |
125 by arbitrary text. To avoid confusion only # comments are recognized. This | |
126 is the same as in shell scripts and Python programs. | |
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127 |
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128 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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129 `:number` for that. > |
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130 101 number |
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131 |
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132 To improve readability there must be a space between a command and the # |
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133 that starts a comment: > |
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134 var name = value # comment |
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135 var name = value# error! |
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136 |
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137 Do not start a comment with #{, it looks like the legacy dictionary literal |
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138 and produces an error where this might be confusing. #{{ or #{{{ are OK, |
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139 these can be used to start a fold. |
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141 In legacy Vim script # is also used for the alternate file name. In Vim9 |
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142 script you need to use %% instead. Instead of ## use %%% (stands for all |
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143 arguments). |
20115 | 144 |
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146 Vim9 functions ~ |
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147 |
20241 | 148 A function defined with `:def` is compiled. Execution is many times faster, |
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149 often 10 to 100 times. |
20241 | 150 |
20552 | 151 Many errors are already found when compiling, before the function is executed. |
20241 | 152 The syntax is strict, to enforce code that is easy to read and understand. |
153 | |
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154 Compilation is done when any of these is encountered: |
23164 | 155 - the first time the function is called |
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156 - when the `:defcompile` command is encountered in the script after the |
21991 | 157 function was defined |
158 - `:disassemble` is used for the function. | |
159 - a function that is compiled calls the function or uses it as a function | |
25700 | 160 reference (so that the argument and return types can be checked) |
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161 *E1091* |
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162 If compilation fails it is not tried again on the next call, instead this |
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163 error is given: "E1091: Function is not compiled: {name}". |
24569 | 164 Compilation will fail when encountering a user command that has not been |
165 created yet. In this case you can call `execute()` to invoke it at runtime. > | |
166 def MyFunc() | |
167 execute('DefinedLater') | |
168 enddef | |
20552 | 169 |
170 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
23164 | 171 "closure". A `:def` function always aborts on an error (unless `:silent!` was |
172 used for the command or inside a `:try` block), does not get a range passed | |
23305 | 173 cannot be a "dict" function, and can always be a closure. |
25700 | 174 *vim9-no-dict-function* |
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175 Later classes will be added, which replaces the "dict function" mechanism. |
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176 For now you will need to pass the dictionary explicitly: > |
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177 def DictFunc(d: dict<any>, arg: string) |
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178 echo d[arg] |
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179 enddef |
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180 var d = {item: 'value', func: DictFunc} |
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181 d.func(d, 'item') |
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182 |
20241 | 183 The argument types and return type need to be specified. The "any" type can |
184 be used, type checking will then be done at runtime, like with legacy | |
185 functions. | |
186 | |
21825 | 187 Arguments are accessed by name, without "a:", just like any other language. |
188 There is no "a:" dictionary or "a:000" list. | |
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189 *vim9-variable-arguments* |
20241 | 190 Variable arguments are defined as the last argument, with a name and have a |
21825 | 191 list type, similar to TypeScript. For example, a list of numbers: > |
22171 | 192 def MyFunc(...itemlist: list<number>) |
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193 for item in itemlist |
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194 ... |
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195 |
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196 When a function argument is optional (it has a default value) passing `v:none` |
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197 as the argument results in using the default value. This is useful when you |
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198 want to specify a value for an argument that comes after an argument that |
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199 should use its default value. Example: > |
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200 def MyFunc(one = 'one', last = 'last) |
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201 ... |
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202 enddef |
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203 MyFunc(v:none, 'LAST') # first argument uses default value 'one' |
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204 < |
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205 *vim9-ignored-argument* |
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206 The argument "_" (an underscore) can be used to ignore the argument. This is |
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207 most useful in callbacks where you don't need it, but do need to give an |
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208 argument to match the call. E.g. when using map() two arguments are passed, |
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209 the key and the value, to ignore the key: > |
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210 map(myList, (_, v) => v * 2) |
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211 There is no error for using the "_" argument multiple times. No type needs to |
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212 be given. |
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213 |
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214 |
20241 | 215 Functions and variables are script-local by default ~ |
20856 | 216 *vim9-scopes* |
20115 | 217 When using `:function` or `:def` to specify a new function at the script level |
218 in a Vim9 script, the function is local to the script, as if "s:" was | |
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219 prefixed. Using the "s:" prefix is optional. To define a global function or |
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220 variable the "g:" prefix must be used. For functions in an autoload script |
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221 the "name#" prefix is sufficient. > |
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222 def ThisFunction() # script-local |
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223 def s:ThisFunction() # script-local |
22171 | 224 def g:ThatFunction() # global |
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225 def scriptname#function() # autoload |
20115 | 226 |
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227 When using `:function` or `:def` to specify a nested function inside a `:def` |
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228 function, this nested function is local to the code block it is defined in. |
22565 | 229 In a `:def` function it is not possible to define a script-local function. It |
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230 is possible to define a global function by using the "g:" prefix. |
20115 | 231 |
232 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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233 search for the function: |
22565 | 234 - in the function scope, in block scopes |
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235 - in the script scope, possibly imported |
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236 - in the list of global functions |
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237 However, it is recommended to always use "g:" to refer to a global function |
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238 for clarity. |
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239 |
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240 Since a script-local function reference can be used without "s:" the name must |
24278 | 241 start with an upper case letter even when using the "s:" prefix. In legacy |
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242 script "s:funcref" could be used, because it could not be referred to with |
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243 "funcref". In Vim9 script it can, therefore "s:Funcref" must be used to avoid |
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244 that the name interferes with builtin functions. |
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245 |
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246 In all cases the function must be defined before used. That is when it is |
22723 | 247 called, when `:defcompile` causes it to be compiled, or when code that calls |
248 it is being compiled (to figure out the return type). | |
20241 | 249 |
21676 | 250 The result is that functions and variables without a namespace can usually be |
20241 | 251 found in the script, either defined there or imported. Global functions and |
21676 | 252 variables could be defined anywhere (good luck finding out where!). |
20115 | 253 |
21825 | 254 Global functions can still be defined and deleted at nearly any time. In |
20317 | 255 Vim9 script script-local functions are defined once when the script is sourced |
20552 | 256 and cannot be deleted or replaced. |
20115 | 257 |
23305 | 258 When compiling a function and a function call is encountered for a function |
259 that is not (yet) defined, the |FuncUndefined| autocommand is not triggered. | |
260 You can use an autoload function if needed, or call a legacy function and have | |
261 |FuncUndefined| triggered there. | |
262 | |
20115 | 263 |
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264 Reloading a Vim9 script clears functions and variables by default ~ |
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265 *vim9-reload* |
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266 When loading a legacy Vim script a second time nothing is removed, the |
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267 commands will replace existing variables and functions and create new ones. |
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268 |
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269 When loading a Vim9 script a second time all existing script-local functions |
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270 and variables are deleted, thus you start with a clean slate. This is useful |
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271 if you are developing a plugin and want to try a new version. If you renamed |
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272 something you don't have to worry about the old name still hanging around. |
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273 |
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274 If you do want to keep items, use: > |
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275 vim9script noclear |
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276 |
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277 You want to use this in scripts that use a `finish` command to bail out at |
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278 some point when loaded again. E.g. when a buffer local option is set: > |
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279 vim9script noclear |
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280 setlocal completefunc=SomeFunc |
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281 if exists('*g:SomeFunc') | finish | endif |
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282 def g:SomeFunc() |
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283 .... |
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284 |
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285 |
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286 Variable declarations with :var, :final and :const ~ |
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287 *vim9-declaration* *:var* |
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288 Local variables need to be declared with `:var`. Local constants need to be |
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289 declared with `:final` or `:const`. We refer to both as "variables" in this |
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290 section. |
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291 |
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292 Variables can be local to a script, function or code block: > |
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293 vim9script |
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294 var script_var = 123 |
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295 def SomeFunc() |
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296 var func_var = script_var |
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297 if cond |
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298 var block_var = func_var |
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299 ... |
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300 |
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301 The variables are only visible in the block where they are defined and nested |
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302 blocks. Once the block ends the variable is no longer accessible: > |
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303 if cond |
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304 var inner = 5 |
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305 else |
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306 var inner = 0 |
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307 endif |
22171 | 308 echo inner # Error! |
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309 |
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310 The declaration must be done earlier: > |
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311 var inner: number |
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312 if cond |
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313 inner = 5 |
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314 else |
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315 inner = 0 |
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316 endif |
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317 echo inner |
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318 |
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319 To intentionally hide a variable from code that follows, a block can be |
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320 used: > |
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321 { |
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322 var temp = 'temp' |
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323 ... |
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324 } |
22171 | 325 echo temp # Error! |
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326 |
25402 | 327 This is especially useful in a user command: > |
328 | |
329 command -range Rename { | |
25619 | 330 var save = @a |
331 @a = 'some expression' | |
332 echo 'do something with ' .. @a | |
333 @a = save | |
334 } | |
25402 | 335 |
336 And with autocommands: > | |
337 | |
338 au BufWritePre *.go { | |
25619 | 339 var save = winsaveview() |
340 silent! exe ':%! some formatting command' | |
341 winrestview(save) | |
342 } | |
25402 | 343 |
344 Although using a :def function probably works better. | |
345 | |
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346 Declaring a variable with a type but without an initializer will initialize to |
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347 zero, false or empty. |
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348 |
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349 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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350 without any command. The same for global, window, tab, buffer and Vim |
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351 variables, because they are not really declared. They can also be deleted |
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352 with `:unlet`. |
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353 |
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354 `:lockvar` does not work on local variables. Use `:const` and `:final` |
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355 instead. |
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356 |
25619 | 357 The `exists()` and `exists_compiled()` functions do not work on local variables |
358 or arguments. | |
25402 | 359 |
24024 | 360 Variables, functions and function arguments cannot shadow previously defined |
361 or imported variables and functions in the same script file. | |
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362 Variables may shadow Ex commands, rename the variable if needed. |
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363 |
24387 | 364 Global variables must be prefixed with "g:", also at the script level. > |
19968 | 365 vim9script |
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366 var script_local = 'text' |
21499 | 367 g:global = 'value' |
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368 var Funcref = g:ThatFunction |
19968 | 369 |
24387 | 370 Global functions must be prefixed with "g:" when defining them, but can be |
371 called without "g:". > | |
372 vim9script | |
373 def g:GlobalFunc(): string | |
374 return 'text' | |
375 enddef | |
376 echo GlobalFunc() | |
377 The "g:" prefix is not needed for auto-load functions. | |
378 | |
25619 | 379 *vim9-function-defined-later* |
380 Although global functions can be called without the "g:" prefix, they must | |
381 exist when compiled. By adding the "g:" prefix the function can be defined | |
382 later. Example: > | |
383 def CallPluginFunc() | |
384 if exists('g:loaded_plugin') | |
385 g:PluginFunc() | |
386 endif | |
387 enddef | |
388 | |
389 If you would do it like this you get an error at compile time that | |
390 "PluginFunc" does not exist, even when "g:loaded_plugin" does not exist: > | |
391 def CallPluginFunc() | |
392 if exists('g:loaded_plugin') | |
393 PluginFunc() # Error - function not found | |
394 endif | |
395 enddef | |
396 | |
397 You can use exists_compiled() to avoid the error, but then the function would | |
398 not be called, even when "g:loaded_plugin" is defined later: > | |
399 def CallPluginFunc() | |
400 if exists_compiled('g:loaded_plugin') | |
401 PluginFunc() # Function may never be called | |
402 endif | |
403 enddef | |
404 | |
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405 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
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406 used to repeat a `:substitute` command. |
24468 | 407 *vim9-unpack-ignore* |
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408 For an unpack assignment the underscore can be used to ignore a list item, |
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409 similar to how a function argument can be ignored: > |
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410 [a, _, c] = theList |
24468 | 411 To ignore any remaining items: > |
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412 [a, b; _] = longList |
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413 |
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414 < *E1092* |
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415 Declaring more than one variable at a time, using the unpack notation, is |
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416 currently not supported: > |
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417 var [v1, v2] = GetValues() # Error! |
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418 That is because the type needs to be inferred from the list item type, which |
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419 isn't that easy. |
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420 |
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421 |
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422 Constants ~ |
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423 *vim9-const* *vim9-final* |
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424 How constants work varies between languages. Some consider a variable that |
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425 can't be assigned another value a constant. JavaScript is an example. Others |
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426 also make the value immutable, thus when a constant uses a list, the list |
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427 cannot be changed. In Vim9 we can use both. |
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428 |
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429 `:const` is used for making both the variable and the value a constant. Use |
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430 this for composite structures that you want to make sure will not be modified. |
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431 Example: > |
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432 const myList = [1, 2] |
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433 myList = [3, 4] # Error! |
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434 myList[0] = 9 # Error! |
24024 | 435 myList->add(3) # Error! |
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436 < *:final* |
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437 `:final` is used for making only the variable a constant, the value can be |
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438 changed. This is well known from Java. Example: > |
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439 final myList = [1, 2] |
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440 myList = [3, 4] # Error! |
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441 myList[0] = 9 # OK |
24024 | 442 myList->add(3) # OK |
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443 |
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444 It is common to write constants as ALL_CAPS, but you don't have to. |
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445 |
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446 The constant only applies to the value itself, not what it refers to. > |
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447 final females = ["Mary"] |
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448 const NAMES = [["John", "Peter"], females] |
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449 NAMES[0] = ["Jack"] # Error! |
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450 NAMES[0][0] = "Jack" # Error! |
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451 NAMES[1] = ["Emma"] # Error! |
23573 | 452 NAMES[1][0] = "Emma" # OK, now females[0] == "Emma" |
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453 |
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454 |
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455 Omitting :call and :eval ~ |
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456 |
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457 Functions can be called without `:call`: > |
22171 | 458 writefile(lines, 'file') |
19303 | 459 Using `:call` is still possible, but this is discouraged. |
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460 |
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461 A method call without `eval` is possible, so long as the start is an |
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462 identifier or can't be an Ex command. For a function either "(" or "->" must |
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463 be following, without a line break. Examples: > |
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464 myList->add(123) |
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465 g:myList->add(123) |
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466 [1, 2, 3]->Process() |
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467 {a: 1, b: 2}->Process() |
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468 "foobar"->Process() |
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469 ("foobar")->Process() |
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470 'foobar'->Process() |
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471 ('foobar')->Process() |
19181
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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472 |
21825 | 473 In the rare case there is ambiguity between a function name and an Ex command, |
21676 | 474 prepend ":" to make clear you want to use the Ex command. For example, there |
475 is both the `:substitute` command and the `substitute()` function. When the | |
476 line starts with `substitute(` this will use the function. Prepend a colon to | |
477 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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478 :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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479 |
25402 | 480 If the expression starts with "!" this is interpreted as a shell command, not |
481 negation of a condition. Thus this is a shell command: > | |
482 !shellCommand->something | |
25700 | 483 Put the expression in parentheses to use the "!" for negation: > |
25402 | 484 (!expression)->Method() |
485 | |
19556
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patch 8.2.0335: no completion for :disassemble
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486 Note that while variables need to be defined before they can be used, |
21825 | 487 functions can be called before being defined. This is required to allow |
488 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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489 since the function has to be looked up by name. And a typo in the function |
21516
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490 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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491 |
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492 |
19968 | 493 Omitting function() ~ |
494 | |
495 A user defined function can be used as a function reference in an expression | |
496 without `function()`. The argument types and return type will then be checked. | |
497 The function must already have been defined. > | |
498 | |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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499 var Funcref = MyFunction |
19968 | 500 |
501 When using `function()` the resulting type is "func", a function with any | |
25161 | 502 number of arguments and any return type (including void). The function can be |
503 defined later. | |
19968 | 504 |
505 | |
23358
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patch 8.2.2222: Vim9: cannot keep script variables when reloading
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|
506 Lambda using => instead of -> ~ |
24387 | 507 *vim9-lambda* |
23318
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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508 In legacy script there can be confusion between using "->" for a method call |
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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|
509 and for a lambda. Also, when a "{" is found the parser needs to figure out if |
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510 it is the start of a lambda or a dictionary, which is now more complicated |
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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|
511 because of the use of argument types. |
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|
512 |
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513 To avoid these problems Vim9 script uses a different syntax for a lambda, |
24888
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patch 8.2.2982: Vim9: future commands are not reserved yet
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514 which is similar to JavaScript: > |
23318
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|
515 var Lambda = (arg) => expression |
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516 |
23358
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|
517 No line break is allowed in the arguments of a lambda up to and including the |
25056 | 518 "=>" (so that Vim can tell the difference between an expression in parentheses |
24911 | 519 and lambda arguments). This is OK: > |
23318
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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|
520 filter(list, (k, v) => |
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521 v > 0) |
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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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522 This does not work: > |
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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523 filter(list, (k, v) |
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524 => v > 0) |
23392
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525 This also does not work: > |
23318
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526 filter(list, (k, |
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|
527 v) => v > 0) |
23392
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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528 But you can use a backslash to concatenate the lines before parsing: > |
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
529 filter(list, (k, |
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530 \ v) |
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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531 \ => v > 0) |
24408
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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532 < *vim9-lambda-arguments* |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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533 In legacy script a lambda could be called with any number of extra arguments, |
96e0b898d5b4
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534 there was no way to warn for not using them. In Vim9 script the number of |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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535 arguments must match. If you do want to accept any arguments, or any further |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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536 arguments, use "..._", which makes the function accept |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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537 |vim9-variable-arguments|. Example: > |
96e0b898d5b4
patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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538 var Callback = (..._) => 'anything' |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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539 echo Callback(1, 2, 3) # displays "anything" |
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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540 |
24387 | 541 < *inline-function* |
23318
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542 Additionally, a lambda can contain statements in {}: > |
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543 var Lambda = (arg) => { |
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544 g:was_called = 'yes' |
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545 return expression |
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546 } |
24387 | 547 This can be useful for a timer, for example: > |
548 var count = 0 | |
549 var timer = timer_start(500, (_) => { | |
550 count += 1 | |
551 echom 'Handler called ' .. count | |
552 }, {repeat: 3}) | |
553 | |
24272
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
554 |
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Bram Moolenaar <Bram@vim.org>
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|
555 The ending "}" must be at the start of a line. It can be followed by other |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
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|
556 characters, e.g.: > |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
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557 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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558 return 'value' |
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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559 }) |
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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|
560 No command can follow the "{", only a comment can be used there. |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
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|
561 |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
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|
562 Rationale: The "}" cannot be after a command because it would require parsing |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
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24150
diff
changeset
|
563 the commands to find it. For consistency with that no command can follow the |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
parents:
24150
diff
changeset
|
564 "{". Unfortunately this means using "() => { command }" does not work, line |
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
565 breaks are always required. |
23318
c76240efdf02
patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
566 |
23737 | 567 *vim9-curly* |
23358
b3142fc0a414
patch 8.2.2222: Vim9: cannot keep script variables when reloading
Bram Moolenaar <Bram@vim.org>
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changeset
|
568 To avoid the "{" of a dictionary literal to be recognized as a statement block |
24024 | 569 wrap it in parentheses: > |
23358
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patch 8.2.2222: Vim9: cannot keep script variables when reloading
Bram Moolenaar <Bram@vim.org>
parents:
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|
570 var Lambda = (arg) => ({key: 42}) |
23318
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patch 8.2.2204: Vim9: using -> both for method and lambda is confusing
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|
571 |
23737 | 572 Also when confused with the start of a command block: > |
573 ({ | |
574 key: value | |
575 })->method() | |
576 | |
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
|
577 |
19999
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
578 Automatic line continuation ~ |
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
579 |
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
parents:
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changeset
|
580 In many cases it is obvious that an expression continues on the next line. In |
23392
517fca70e084
patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
581 those cases there is no need to prefix the line with a backslash (see |
517fca70e084
patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
Bram Moolenaar <Bram@vim.org>
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|
582 |line-continuation|). For example, when a list spans multiple lines: > |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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changeset
|
583 var mylist = [ |
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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|
584 'one', |
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patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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585 'two', |
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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|
586 ] |
20011
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
587 And when a dict spans multiple lines: > |
22936
00b0275ffe7f
patch 8.2.2015: Vim9: literal dict #{} is not like any other language
Bram Moolenaar <Bram@vim.org>
parents:
22723
diff
changeset
|
588 var mydict = { |
20011
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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|
589 one: 1, |
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
590 two: 2, |
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
591 } |
24888
b6ac4ed5e2d2
patch 8.2.2982: Vim9: future commands are not reserved yet
Bram Moolenaar <Bram@vim.org>
parents:
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changeset
|
592 With a function call: > |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
Bram Moolenaar <Bram@vim.org>
parents:
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|
593 var result = Func( |
20011
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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changeset
|
594 arg1, |
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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diff
changeset
|
595 arg2 |
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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diff
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|
596 ) |
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
parents:
19999
diff
changeset
|
597 |
20982
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
parents:
20965
diff
changeset
|
598 For binary operators in expressions not in [], {} or () a line break is |
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
599 possible just before or after the operator. For example: > |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
600 var text = lead |
20982
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patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
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changeset
|
601 .. middle |
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
parents:
20965
diff
changeset
|
602 .. end |
22391
a9fb7efa31d6
patch 8.2.1744: Vim9: using ":const!" is weird
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
603 var total = start + |
23573 | 604 end - |
20013
bf377a9ffccb
patch 8.2.0562: Vim9: cannot split an expression into multiple lines
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
605 correction |
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
Bram Moolenaar <Bram@vim.org>
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changeset
|
606 var result = positive |
20982
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
607 ? PosFunc(arg) |
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
parents:
20965
diff
changeset
|
608 : NegFunc(arg) |
20013
bf377a9ffccb
patch 8.2.0562: Vim9: cannot split an expression into multiple lines
Bram Moolenaar <Bram@vim.org>
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changeset
|
609 |
21499 | 610 For a method call using "->" and a member using a dot, a line break is allowed |
611 before it: > | |
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612 var result = GetBuilder() |
20965 | 613 ->BuilderSetWidth(333) |
614 ->BuilderSetHeight(777) | |
615 ->BuilderBuild() | |
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616 var result = MyDict |
21499 | 617 .member |
20965 | 618 |
23392
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619 For commands that have an argument that is a list of commands, the | character |
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620 at the start of the line indicates line continuation: > |
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621 autocmd BufNewFile *.match if condition |
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622 | echo 'match' |
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623 | endif |
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624 |
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625 Note that this means that in heredoc the first line cannot be a bar: > |
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626 var lines =<< trim END |
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627 | this doesn't work |
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628 END |
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629 Either use an empty line at the start or do not use heredoc. Or temporarily |
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630 add the "C" flag to 'cpoptions': > |
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631 set cpo+=C |
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632 var lines =<< trim END |
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633 | this doesn't work |
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634 END |
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635 set cpo-=C |
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636 If the heredoc is inside a function 'cpoptions' must be set before :def and |
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637 restored after the :enddef. |
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638 |
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639 In places where line continuation with a backslash is still needed, such as |
25161 | 640 splitting up a long Ex command, comments can start with '#\ ': > |
641 syn region Text | |
24888
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642 \ start='foo' |
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643 #\ comment |
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644 \ end='bar' |
25161 | 645 Like with legacy script '"\ ' is used. This is also needed when line |
646 continuation is used without a backslash and a line starts with a bar: > | |
647 au CursorHold * echom 'BEFORE bar' | |
648 #\ some comment | |
649 | echom 'AFTER bar' | |
650 < | |
651 *E1050* | |
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652 To make it possible for the operator at the start of the line to be |
24888
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653 recognized, it is required to put a colon before a range. This example will |
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654 add "start" and print: > |
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655 var result = start |
20982
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|
656 + print |
21250 | 657 Like this: > |
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658 var result = start + print |
21250 | 659 |
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660 This will assign "start" and print a line: > |
22391
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661 var result = start |
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662 :+ print |
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
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663 |
23047 | 664 Note that the colon is not required for the |+cmd| argument: > |
665 edit +6 fname | |
666 | |
20015
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patch 8.2.0563: Vim9: cannot split a function line
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|
667 It is also possible to split a function header over multiple lines, in between |
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668 arguments: > |
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patch 8.2.0563: Vim9: cannot split a function line
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669 def MyFunc( |
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670 text: string, |
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671 separator = '-' |
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672 ): string |
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673 |
23305 | 674 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
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675 has been made stricter. E.g., because of the error in the first line, the |
23305 | 676 second line is seen as a separate command: > |
677 popup_create(some invalid expression, { | |
678 exit_cb: Func}) | |
679 Now "exit_cb: Func})" is actually a valid command: save any changes to the | |
680 file "_cb: Func})" and exit. To avoid this kind of mistake in Vim9 script | |
681 there must be white space between most command names and the argument. | |
682 | |
23666 | 683 However, the argument of a command that is a command won't be recognized. For |
684 example, after "windo echo expr" a line break inside "expr" will not be seen. | |
685 | |
23305 | 686 |
21250 | 687 Notes: |
688 - "enddef" cannot be used at the start of a continuation line, it ends the | |
689 current function. | |
690 - No line break is allowed in the LHS of an assignment. Specifically when | |
691 unpacking a list |:let-unpack|. This is OK: > | |
22171 | 692 [var1, var2] = |
21250 | 693 Func() |
694 < This does not work: > | |
22171 | 695 [var1, |
21250 | 696 var2] = |
697 Func() | |
698 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
699 similar commands. This is OK: > | |
22171 | 700 echo [1, |
21250 | 701 2] [3, |
702 4] | |
703 < This does not work: > | |
22171 | 704 echo [1, 2] |
21250 | 705 [3, 4] |
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706 - In some cases it is difficult for Vim to parse a command, especially when |
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707 commands are used as an argument to another command, such as `windo`. In |
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|
708 those cases the line continuation with a backslash has to be used. |
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709 |
24569 | 710 |
711 White space ~ | |
712 | |
713 Vim9 script enforces proper use of white space. This is no longer allowed: > | |
714 var name=234 # Error! | |
715 var name= 234 # Error! | |
716 var name =234 # Error! | |
717 There must be white space before and after the "=": > | |
718 var name = 234 # OK | |
719 White space must also be put before the # that starts a comment after a | |
720 command: > | |
721 var name = 234# Error! | |
722 var name = 234 # OK | |
723 | |
724 White space is required around most operators. | |
725 | |
726 White space is required in a sublist (list slice) around the ":", except at | |
727 the start and end: > | |
728 otherlist = mylist[v : count] # v:count has a different meaning | |
729 otherlist = mylist[:] # make a copy of the List | |
730 otherlist = mylist[v :] | |
731 otherlist = mylist[: v] | |
732 | |
733 White space is not allowed: | |
734 - Between a function name and the "(": > | |
735 Func (arg) # Error! | |
736 Func | |
737 \ (arg) # Error! | |
738 Func | |
739 (arg) # Error! | |
740 Func(arg) # OK | |
741 Func( | |
742 arg) # OK | |
743 Func( | |
744 arg # OK | |
745 ) | |
746 | |
25700 | 747 White space is not allowed in a `:set` command between the option name and a |
748 following "&", "!", "<", "=", "+=", "-=" or "^=". | |
25402 | 749 |
24569 | 750 |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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751 No curly braces expansion ~ |
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752 |
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|
753 |curly-braces-names| cannot be used. |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
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|
754 |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
755 |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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756 Dictionary literals ~ |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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|
757 |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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|
758 Traditionally Vim has supported dictionary literals with a {} syntax: > |
00b0275ffe7f
patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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|
759 let dict = {'key': value} |
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|
760 |
23088
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
Bram Moolenaar <Bram@vim.org>
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changeset
|
761 Later it became clear that using a simple text key is very common, thus |
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
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|
762 literal dictionaries were introduced in a backwards compatible way: > |
22936
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|
763 let dict = #{key: value} |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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764 |
23088
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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|
765 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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|
766 that using a literal key is much more common than using an expression, and |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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|
767 considering that JavaScript uses this syntax, using the {} form for dictionary |
23088
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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changeset
|
768 literals is considered a much more useful syntax. In Vim9 script the {} form |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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changeset
|
769 uses literal keys: > |
23666 | 770 var dict = {key: value} |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
Bram Moolenaar <Bram@vim.org>
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changeset
|
771 |
23088
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
772 This works for alphanumeric characters, underscore and dash. If you want to |
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
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changeset
|
773 use another character, use a single or double quoted string: > |
23666 | 774 var dict = {'key with space': value} |
775 var dict = {"key\twith\ttabs": value} | |
776 var dict = {'': value} # empty key | |
23088
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Bram Moolenaar <Bram@vim.org>
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|
777 |
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Bram Moolenaar <Bram@vim.org>
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changeset
|
778 In case the key needs to be an expression, square brackets can be used, just |
285cde4b8d0e
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Bram Moolenaar <Bram@vim.org>
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|
779 like in JavaScript: > |
23666 | 780 var dict = {["key" .. nr]: value} |
22936
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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diff
changeset
|
781 |
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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changeset
|
782 The key type can be string, number, bool or float. Other types result in an |
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
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changeset
|
783 error. A number can be given with and without the []: > |
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
784 var dict = {123: 'without', [456]: 'with'} |
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
785 echo dict |
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
786 {'456': 'with', '123': 'without'} |
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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|
787 |
22936
00b0275ffe7f
patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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|
788 |
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
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changeset
|
789 No :xit, :t, :k, :append, :change or :insert ~ |
19303 | 790 |
21584
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
Bram Moolenaar <Bram@vim.org>
parents:
21550
diff
changeset
|
791 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>
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changeset
|
792 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>
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diff
changeset
|
793 Instead of `:t` you can use `:copy`. |
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
parents:
23974
diff
changeset
|
794 Instead of `:k` you can use `:mark`. |
19181
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795 |
19303 | 796 |
797 Comparators ~ | |
798 | |
799 The 'ignorecase' option is not used for comparators that use strings. | |
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800 |
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801 |
24569 | 802 Abort after error ~ |
803 | |
804 In legacy script, when an error is encountered, Vim continues to execute | |
805 following lines. This can lead to a long sequence of errors and need to type | |
806 CTRL-C to stop it. In Vim9 script execution of commands stops at the first | |
807 error. Example: > | |
808 vim9script | |
809 var x = does-not-exist | |
810 echo 'not executed' | |
811 | |
812 | |
23666 | 813 For loop ~ |
814 | |
815 Legacy Vim script has some tricks to make a for loop over a list handle | |
816 deleting items at the current or previous item. In Vim9 script it just uses | |
817 the index, if items are deleted then items in the list will be skipped. | |
818 Example legacy script: > | |
819 let l = [1, 2, 3, 4] | |
820 for i in l | |
821 echo i | |
822 call remove(l, index(l, i)) | |
823 endfor | |
824 Would echo: | |
825 1 | |
826 2 | |
827 3 | |
828 4 | |
829 In compiled Vim9 script you get: | |
830 1 | |
831 3 | |
832 Generally, you should not change the list that is iterated over. Make a copy | |
833 first if needed. | |
834 | |
835 | |
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836 Conditions and expressions ~ |
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837 |
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838 Conditions and expressions are mostly working like they do in other languages. |
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839 Some values are different from legacy Vim script: |
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840 value legacy Vim script Vim9 script ~ |
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841 0 falsy falsy |
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842 1 truthy truthy |
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843 99 truthy Error! |
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844 "0" falsy Error! |
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845 "99" truthy Error! |
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846 "text" falsy Error! |
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847 |
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848 For the "??" operator and when using "!" then there is no error, every value |
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849 is either falsy or truthy. This is mostly like JavaScript, except that an |
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850 empty list and dict is falsy: |
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851 |
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852 type truthy when ~ |
23466 | 853 bool true, v:true or 1 |
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854 number non-zero |
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855 float non-zero |
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856 string non-empty |
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857 blob non-empty |
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858 list non-empty (different from JavaScript) |
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859 dictionary non-empty (different from JavaScript) |
19968 | 860 func when there is a function name |
23466 | 861 special true or v:true |
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862 job when not NULL |
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863 channel when not NULL |
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864 class when not NULL |
23466 | 865 object when not NULL (TODO: when isTrue() returns true) |
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866 |
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867 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
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868 one: > |
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869 1 || false == true |
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870 0 || 1 == true |
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871 0 || false == false |
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872 1 && true == true |
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873 0 && 1 == false |
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874 8 || 0 Error! |
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875 'yes' && 0 Error! |
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876 [] || 99 Error! |
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877 |
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878 When using "!" for inverting, there is no error for using any type and the |
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879 result is a boolean. "!!" can be used to turn any value into boolean: > |
23573 | 880 !'yes' == false |
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881 !![] == false |
23573 | 882 !![1, 2, 3] == true |
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883 |
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884 When using "`.."` for string concatenation arguments of simple types are |
22500
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885 always converted to string: > |
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886 'hello ' .. 123 == 'hello 123' |
23466 | 887 'hello ' .. v:true == 'hello true' |
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888 |
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889 Simple types are string, float, special and bool. For other types |string()| |
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890 can be used. |
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891 *false* *true* *null* |
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892 In Vim9 script one can use "true" for v:true, "false" for v:false and "null" |
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893 for v:null. When converting a boolean to a string "false" and "true" are |
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894 used, not "v:false" and "v:true" like in legacy script. "v:none" is not |
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895 changed, it is only used in JSON and has no equivalent in other languages. |
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896 |
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897 Indexing a string with [idx] or taking a slice with [idx : idx] uses character |
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898 indexes instead of byte indexes. Composing characters are included. |
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899 Example: > |
21825 | 900 echo 'bár'[1] |
901 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
902 script this results in the string 'á'. | |
23573 | 903 A negative index is counting from the end, "[-1]" is the last character. |
23666 | 904 To exclude the last character use |slice()|. |
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905 To count composing characters separately use |strcharpart()|. |
23573 | 906 If the index is out of range then an empty string results. |
907 | |
908 In legacy script "++var" and "--var" would be silently accepted and have no | |
909 effect. This is an error in Vim9 script. | |
910 | |
911 Numbers starting with zero are not considered to be octal, only numbers | |
912 starting with "0o" are octal: "0o744". |scriptversion-4| | |
21825 | 913 |
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914 |
21093 | 915 What to watch out for ~ |
916 *vim9-gotchas* | |
917 Vim9 was designed to be closer to often used programming languages, but at the | |
918 same time tries to support the legacy Vim commands. Some compromises had to | |
919 be made. Here is a summary of what might be unexpected. | |
920 | |
921 Ex command ranges need to be prefixed with a colon. > | |
23666 | 922 -> legacy Vim: shifts the previous line to the right |
923 ->func() Vim9: method call in a continuation line | |
924 :-> Vim9: shifts the previous line to the right | |
21093 | 925 |
23666 | 926 %s/a/b legacy Vim: substitute on all lines |
21093 | 927 x = alongname |
23666 | 928 % another Vim9: modulo operator in a continuation line |
929 :%s/a/b Vim9: substitute on all lines | |
930 't legacy Vim: jump to mark t | |
931 'text'->func() Vim9: method call | |
932 :'t Vim9: jump to mark t | |
21093 | 933 |
21676 | 934 Some Ex commands can be confused with assignments in Vim9 script: > |
23666 | 935 g:name = value # assignment |
936 g:pattern:cmd # invalid command - ERROR | |
937 :g:pattern:cmd # :global command | |
21676 | 938 |
21093 | 939 Functions defined with `:def` compile the whole function. Legacy functions |
940 can bail out, and the following lines are not parsed: > | |
941 func Maybe() | |
942 if !has('feature') | |
943 return | |
944 endif | |
945 use-feature | |
946 endfunc | |
947 Vim9 functions are compiled as a whole: > | |
948 def Maybe() | |
949 if !has('feature') | |
950 return | |
951 endif | |
23573 | 952 use-feature # May give a compilation error |
21093 | 953 enddef |
954 For a workaround, split it in two functions: > | |
955 func Maybe() | |
956 if has('feature') | |
23666 | 957 call MaybeInner() |
21093 | 958 endif |
959 endfunc | |
960 if has('feature') | |
961 def MaybeInner() | |
962 use-feature | |
963 enddef | |
964 endif | |
22171 | 965 Or put the unsupported code inside an `if` with a constant expression that |
21991 | 966 evaluates to false: > |
967 def Maybe() | |
968 if has('feature') | |
969 use-feature | |
970 endif | |
971 enddef | |
25619 | 972 The `exists_compiled()` function can also be used for this. |
973 *vim9-user-command* | |
23666 | 974 Another side effect of compiling a function is that the presence of a user |
23573 | 975 command is checked at compile time. If the user command is defined later an |
976 error will result. This works: > | |
977 command -nargs=1 MyCommand echom <q-args> | |
978 def Works() | |
979 MyCommand 123 | |
980 enddef | |
981 This will give an error for "MyCommand" not being defined: > | |
982 def Works() | |
983 command -nargs=1 MyCommand echom <q-args> | |
984 MyCommand 123 | |
985 enddef | |
986 A workaround is to invoke the command indirectly with `:execute`: > | |
987 def Works() | |
988 command -nargs=1 MyCommand echom <q-args> | |
989 execute 'MyCommand 123' | |
990 enddef | |
991 | |
21991 | 992 Note that for unrecognized commands there is no check for "|" and a following |
993 command. This will give an error for missing `endif`: > | |
994 def Maybe() | |
995 if has('feature') | use-feature | endif | |
996 enddef | |
21093 | 997 |
23305 | 998 Other differences ~ |
999 | |
1000 Patterns are used like 'magic' is set, unless explicitly overruled. | |
1001 The 'edcompatible' option value is not used. | |
1002 The 'gdefault' option value is not used. | |
1003 | |
24387 | 1004 You may also find this wiki useful. It was written by an early adopter of |
24103 | 1005 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
23305 | 1006 |
25056 | 1007 *:++* *:--* |
1008 The ++ and -- commands have been added. They are very similar to adding or | |
1009 subtracting one: > | |
1010 ++var | |
1011 var += 1 | |
1012 --var | |
1013 var -= 1 | |
1014 | |
1015 Using ++var or --var in an expression is not supported yet. | |
1016 | |
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1017 ============================================================================== |
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1018 |
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1019 3. New style functions *fast-functions* |
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1020 |
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1021 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1022 |
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1023 *:def* |
21825 | 1024 :def[!] {name}([arguments])[: {return-type}] |
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1025 Define a new function by the name {name}. The body of |
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1026 the function follows in the next lines, until the |
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1027 matching `:enddef`. |
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1028 |
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1029 When {return-type} is omitted or is "void" the |
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1030 function is not expected to return anything. |
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1031 |
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1032 {arguments} is a sequence of zero or more argument |
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1033 declarations. There are three forms: |
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1034 {name}: {type} |
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1035 {name} = {value} |
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1036 {name}: {type} = {value} |
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1037 The first form is a mandatory argument, the caller |
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1038 must always provide them. |
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1039 The second and third form are optional arguments. |
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1040 When the caller omits an argument the {value} is used. |
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1041 |
20856 | 1042 The function will be compiled into instructions when |
21499 | 1043 called, or when `:disassemble` or `:defcompile` is |
1044 used. Syntax and type errors will be produced at that | |
1045 time. | |
20856 | 1046 |
21499 | 1047 It is possible to nest `:def` inside another `:def` or |
1048 `:function` up to about 50 levels deep. | |
19303 | 1049 |
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1050 [!] is used as with `:function`. Note that |
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1051 script-local functions cannot be deleted or redefined |
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1052 later in Vim9 script. They can only be removed by |
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1053 reloading the same script. |
19181
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1054 |
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1055 *:enddef* |
21499 | 1056 :enddef End of a function defined with `:def`. It should be on |
1057 a line by its own. | |
19181
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1058 |
24387 | 1059 You may also find this wiki useful. It was written by an early adopter of |
24128
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1060 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
19181
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1061 |
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1062 If the script the function is defined in is Vim9 script, then script-local |
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1063 variables can be accessed without the "s:" prefix. They must be defined |
20856 | 1064 before the function is compiled. If the script the function is defined in is |
1065 legacy script, then script-local variables must be accessed with the "s:" | |
24387 | 1066 prefix if they do not exist at the time of compiling. |
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1067 |
20552 | 1068 *:defc* *:defcompile* |
1069 :defc[ompile] Compile functions defined in the current script that | |
1070 were not compiled yet. | |
1071 This will report errors found during the compilation. | |
19473
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1072 |
19404 | 1073 *:disa* *:disassemble* |
1074 :disa[ssemble] {func} Show the instructions generated for {func}. | |
1075 This is for debugging and testing. | |
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1076 Note that for command line completion of {func} you |
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1077 can prepend "s:" to find script-local functions. |
19404 | 1078 |
24911 | 1079 :disa[ssemble] profile {func} |
1080 Like `:disassemble` but with the instructions used for | |
23737 | 1081 profiling. |
1082 | |
24911 | 1083 :disa[ssemble] debug {func} |
1084 Like `:disassemble` but with the instructions used for | |
1085 debugging. | |
1086 | |
21250 | 1087 Limitations ~ |
1088 | |
1089 Local variables will not be visible to string evaluation. For example: > | |
23358
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1090 def MapList(): list<string> |
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1091 var list = ['aa', 'bb', 'cc', 'dd'] |
21250 | 1092 return range(1, 2)->map('list[v:val]') |
1093 enddef | |
1094 | |
1095 The map argument is a string expression, which is evaluated without the | |
1096 function scope. Instead, use a lambda: > | |
23358
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1097 def MapList(): list<string> |
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1098 var list = ['aa', 'bb', 'cc', 'dd'] |
23358
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1099 return range(1, 2)->map(( _, v) => list[v]) |
21250 | 1100 enddef |
1101 | |
23358
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1102 The same is true for commands that are not compiled, such as `:global`. |
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1103 For these the backtick expansion can be used. Example: > |
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1104 def Replace() |
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1105 var newText = 'blah' |
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1106 g/pattern/s/^/`=newText`/ |
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1107 enddef |
21250 | 1108 |
25402 | 1109 Or a script variable can be used: > |
1110 var newText = 'blah' | |
1111 def Replace() | |
1112 g/pattern/s/^/\=newText/ | |
1113 enddef | |
1114 | |
24278 | 1115 Closures defined in a loop will share the same context. For example: > |
1116 var flist: list<func> | |
25402 | 1117 for i in range(5) |
24278 | 1118 var inloop = i |
1119 flist[i] = () => inloop | |
1120 endfor | |
25402 | 1121 echo range(5)->map((i, _) => flist[i]()) |
1122 # Result: [4, 4, 4, 4, 4] | |
24278 | 1123 |
1124 The "inloop" variable will exist only once, all closures put in the list refer | |
25402 | 1125 to the same instance, which in the end will have the value 4. This is |
1126 efficient, also when looping many times. If you do want a separate context | |
1127 for each closure call a function to define it: > | |
1128 def GetClosure(i: number): func | |
1129 var infunc = i | |
1130 return () => infunc | |
24278 | 1131 enddef |
1132 | |
1133 var flist: list<func> | |
25402 | 1134 for i in range(5) |
1135 flist[i] = GetClosure(i) | |
24278 | 1136 endfor |
25402 | 1137 echo range(5)->map((i, _) => flist[i]()) |
1138 # Result: [0, 1, 2, 3, 4] | |
24278 | 1139 |
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1140 ============================================================================== |
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1141 |
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1142 4. Types *vim9-types* |
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1143 |
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1144 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1145 |
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1146 The following builtin types are supported: |
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1147 bool |
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1148 number |
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1149 float |
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1150 string |
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1151 blob |
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1152 list<{type}> |
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1153 dict<{type}> |
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1154 job |
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1155 channel |
19646 | 1156 func |
19968 | 1157 func: {type} |
19904
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1158 func({type}, ...) |
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1159 func({type}, ...): {type} |
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1160 |
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1161 Not supported yet: |
19904
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1162 tuple<a: {type}, b: {type}, ...> |
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1163 |
25161 | 1164 These types can be used in declarations, but no simple value will actually |
1165 have the "void" type. | |
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1166 |
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1167 There is no array type, use list<{type}> instead. For a list constant an |
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1168 efficient implementation is used that avoids allocating lot of small pieces of |
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1169 memory. |
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1170 |
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1171 A partial and function can be declared in more or less specific ways: |
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1172 func any kind of function reference, no type |
19968 | 1173 checking for arguments or return value |
25161 | 1174 func: void any number and type of arguments, no return |
1175 value | |
19904
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1176 func: {type} any number and type of arguments with specific |
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1177 return type |
25161 | 1178 |
1179 func() function with no argument, does not return a | |
1180 value | |
1181 func(): void same | |
1182 func(): {type} function with no argument and return type | |
1183 | |
19968 | 1184 func({type}) function with argument type, does not return |
19904
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1185 a value |
19968 | 1186 func({type}): {type} function with argument type and return type |
1187 func(?{type}) function with type of optional argument, does | |
1188 not return a value | |
1189 func(...{type}) function with type of variable number of | |
1190 arguments, does not return a value | |
1191 func({type}, ?{type}, ...{type}): {type} | |
1192 function with: | |
1193 - type of mandatory argument | |
1194 - type of optional argument | |
1195 - type of variable number of arguments | |
1196 - return type | |
19904
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1197 |
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1198 If the return type is "void" the function does not return a value. |
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1199 |
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1200 The reference can also be a |Partial|, in which case it stores extra arguments |
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1201 and/or a dictionary, which are not visible to the caller. Since they are |
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1202 called in the same way the declaration is the same. |
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1203 |
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1204 Custom types can be defined with `:type`: > |
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1205 :type MyList list<string> |
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1206 Custom types must start with a capital letter, to avoid name clashes with |
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1207 builtin types added later, similarly to user functions. |
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1208 {not implemented yet} |
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1209 |
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1210 And classes and interfaces can be used as types: > |
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1211 :class MyClass |
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1212 :var mine: MyClass |
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1213 |
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1214 :interface MyInterface |
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1215 :var mine: MyInterface |
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1216 |
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1217 :class MyTemplate<Targ> |
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1218 :var mine: MyTemplate<number> |
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1219 :var mine: MyTemplate<string> |
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1220 |
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1221 :class MyInterface<Targ> |
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1222 :var mine: MyInterface<number> |
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1223 :var mine: MyInterface<string> |
19181
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1224 {not implemented yet} |
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1225 |
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1226 |
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1227 Variable types and type casting ~ |
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1228 *variable-types* |
21717
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1229 Variables declared in Vim9 script or in a `:def` function have a type, either |
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1230 specified explicitly or inferred from the initialization. |
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1231 |
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1232 Global, buffer, window and tab page variables do not have a specific type, the |
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1233 value can be changed at any time, possibly changing the type. Therefore, in |
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1234 compiled code the "any" type is assumed. |
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1235 |
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1236 This can be a problem when the "any" type is undesired and the actual type is |
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1237 expected to always be the same. For example, when declaring a list: > |
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1238 var l: list<number> = [1, g:two] |
23305 | 1239 At compile time Vim doesn't know the type of "g:two" and the expression type |
1240 becomes list<any>. An instruction is generated to check the list type before | |
1241 doing the assignment, which is a bit inefficient. | |
1242 *type-casting* | |
1243 To avoid this, use a type cast: > | |
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1244 var l: list<number> = [1, <number>g:two] |
23305 | 1245 The compiled code will then only check that "g:two" is a number and give an |
1246 error if it isn't. This is called type casting. | |
21717
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1247 |
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1248 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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1249 after the "<" or before the ">" (to avoid them being confused with |
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1250 smaller-than and bigger-than operators). |
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1251 |
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1252 The semantics is that, if needed, a runtime type check is performed. The |
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1253 value is not actually changed. If you need to change the type, e.g. to change |
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1254 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
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1255 string to a number. |
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1256 |
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1257 |
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1258 Type inference ~ |
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1259 *type-inference* |
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1260 In general: Whenever the type is clear it can be omitted. For example, when |
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1261 declaring a variable and giving it a value: > |
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1262 var name = 0 # infers number type |
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1263 var name = 'hello' # infers string type |
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1264 |
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1265 The type of a list and dictionary comes from the common type of the values. |
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1266 If the values all have the same type, that type is used for the list or |
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1267 dictionary. If there is a mix of types, the "any" type is used. > |
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1268 [1, 2, 3] list<number> |
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1269 ['a', 'b', 'c'] list<string> |
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1270 [1, 'x', 3] list<any> |
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1271 |
25161 | 1272 The common type of function references, if they do not all have the same |
1273 number of arguments, uses "(...)" to indicate the number of arguments is not | |
1274 specified. For example: > | |
1275 def Foo(x: bool) | |
1276 enddef | |
1277 def Bar(x: bool, y: bool) | |
1278 enddef | |
1279 var funclist = [Foo, Bar] | |
1280 echo funclist->typename() | |
1281 Results in: | |
1282 list<func(...)> | |
1283 | |
24387 | 1284 For script-local variables in Vim9 script the type is checked, also when the |
1285 variable was declared in a legacy function. | |
1286 | |
21991 | 1287 |
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1288 Stricter type checking ~ |
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1289 *type-checking* |
21991 | 1290 In legacy Vim script, where a number was expected, a string would be |
1291 automatically converted to a number. This was convenient for an actual number | |
24387 | 1292 such as "123", but leads to unexpected problems (and no error message) if the |
21991 | 1293 string doesn't start with a number. Quite often this leads to hard-to-find |
1294 bugs. | |
1295 | |
1296 In Vim9 script this has been made stricter. In most places it works just as | |
22171 | 1297 before, if the value used matches the expected type. There will sometimes be |
1298 an error, thus breaking backwards compatibility. For example: | |
21991 | 1299 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
25161 | 1300 - Using a string value when setting a number option. |
21991 | 1301 - Using a number where a string is expected. *E1024* |
1302 | |
23573 | 1303 One consequence is that the item type of a list or dict given to map() must |
24024 | 1304 not change. This will give an error in Vim9 script: > |
25161 | 1305 vim9 echo map([1, 2, 3], (i, v) => 'item ' .. i) |
24024 | 1306 E1012: Type mismatch; expected number but got string |
25161 | 1307 Instead use |mapnew(): > |
1308 vim9 echo mapnew([1, 2, 3], (i, v) => 'item ' .. i) | |
1309 ['item 0', 'item 1', 'item 2'] | |
1310 | |
1311 If the item type was determined to be "any" it can change to a more specific | |
1312 type. E.g. when a list of mixed types gets changed to a list of numbers: > | |
1313 var mylist = [1, 2.0, '3'] | |
1314 # typename(mylist) == "list<any>" | |
1315 map(mylist, (i, v) => 'item ' .. i) | |
1316 # typename(mylist) == "list<string>", no error | |
1317 | |
24024 | 1318 Same for |extend()|, use |extendnew()| instead, and for |flatten()|, use |
1319 |flattennew()| instead. | |
23573 | 1320 |
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1321 ============================================================================== |
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1322 |
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1323 5. Namespace, Import and Export |
19181
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1324 *vim9script* *vim9-export* *vim9-import* |
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1325 |
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1326 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1327 |
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1328 A Vim9 script can be written to be imported. This means that everything in |
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1329 the script is local, unless exported. Those exported items, and only those |
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1330 items, can then be imported in another script. |
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1331 |
21991 | 1332 You can cheat by using the global namespace explicitly. We will assume here |
1333 that you don't do that. | |
1334 | |
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1335 |
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1336 Namespace ~ |
23392
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1337 *vim9-namespace* |
19303 | 1338 To recognize a file that can be imported the `vim9script` statement must |
23974
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1339 appear as the first statement in the file (see |vim9-mix| for an exception). |
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1340 It tells Vim to interpret the script in its own namespace, instead of the |
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1341 global namespace. If a file starts with: > |
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1342 vim9script |
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1343 var myvar = 'yes' |
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1344 Then "myvar" will only exist in this file. While without `vim9script` it would |
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1345 be available as `g:myvar` from any other script and function. |
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1346 |
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1347 The variables at the file level are very much like the script-local "s:" |
20115 | 1348 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
1349 deleted. | |
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1350 |
20115 | 1351 In Vim9 script the global "g:" namespace can still be used as before. And the |
1352 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
1353 declared and they can be deleted. | |
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1354 |
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1355 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
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1356 Vim default value, like with: > |
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1357 :set cpo&vim |
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1358 One of the effects is that |line-continuation| is always enabled. |
24150
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1359 The original value of 'cpoptions' is restored at the end of the script, while |
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1360 flags added or removed in the script are also added to or removed from the |
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1361 original value to get the same effect. The order of flags may change. |
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1362 |
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1363 *vim9-mix* |
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1364 There is one way to use both legacy and Vim9 syntax in one script file: > |
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1365 " comments may go here |
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1366 if !has('vim9script') |
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1367 " legacy script commands go here |
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1368 finish |
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1369 endif |
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1370 vim9script |
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1371 # Vim9 script commands go here |
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1372 This allows for writing a script that takes advantage of the Vim9 script |
24024 | 1373 syntax if possible, but will also work on a Vim version without it. |
23974
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1374 |
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1375 This can only work in two ways: |
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|
1376 1. The "if" statement evaluates to false, the commands up to `endif` are |
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|
1377 skipped and `vim9script` is then the first command actually executed. |
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|
1378 2. The "if" statement evaluates to true, the commands up to `endif` are |
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|
1379 executed and `finish` bails out before reaching `vim9script`. |
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1380 |
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|
1381 TODO: The "vim9script" feature does not exist yet, it will only be added once |
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|
1382 the Vim9 script syntax has been fully implemented. |
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1383 |
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1384 |
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|
1385 Export ~ |
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1386 *:export* *:exp* |
21499 | 1387 Exporting an item can be written as: > |
19181
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1388 export const EXPORTED_CONST = 1234 |
22391
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1389 export var someValue = ... |
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1390 export final someValue = ... |
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|
1391 export const someValue = ... |
19181
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1392 export def MyFunc() ... |
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1393 export class MyClass ... |
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1394 export interface MyClass ... |
19181
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1395 |
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|
1396 As this suggests, only constants, variables, `:def` functions and classes can |
24888
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|
1397 be exported. {not implemented yet: class, interface} |
19181
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1398 |
20856 | 1399 *E1042* |
1400 `:export` can only be used in Vim9 script, at the script level. | |
19181
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1401 |
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1402 |
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1403 Import ~ |
20965 | 1404 *:import* *:imp* *E1094* |
19181
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1405 The exported items can be imported individually in another Vim9 script: > |
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|
1406 import EXPORTED_CONST from "thatscript.vim" |
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1407 import MyClass from "myclass.vim" |
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1408 |
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1409 To import multiple items at the same time: > |
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|
1410 import {someValue, MyClass} from "thatscript.vim" |
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1411 |
19303 | 1412 In case the name is ambiguous, another name can be specified: > |
19181
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1413 import MyClass as ThatClass from "myclass.vim" |
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1414 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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1415 |
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|
1416 To import all exported items under a specific identifier: > |
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|
1417 import * as That from 'thatscript.vim' |
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1418 |
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|
1419 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
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1420 to choose the name "That", but it is highly recommended to use the name of the |
25773 | 1421 script file to avoid confusion. Also avoid command names, because the name |
1422 will shadow them. | |
19181
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1423 |
22171 | 1424 `:import` can also be used in legacy Vim script. The imported items still |
1425 become script-local, even when the "s:" prefix is not given. | |
1426 | |
25282
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|
1427 `:import` can not be used in a function. Imported items are intended to exist |
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|
1428 at the script level and only imported once. |
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1429 |
19181
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1430 The script name after `import` can be: |
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1431 - A relative path, starting "." or "..". This finds a file relative to the |
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|
1432 location of the script file itself. This is useful to split up a large |
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|
1433 plugin into several files. |
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1434 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
22723 | 1435 will rarely be used. |
19181
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1436 - A path not being relative or absolute. This will be found in the |
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|
1437 "import" subdirectories of 'runtimepath' entries. The name will usually be |
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1438 longer and unique, to avoid loading the wrong file. |
25619 | 1439 Note that "after/import" is not used. |
19181
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1440 |
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1441 Once a vim9 script file has been imported, the result is cached and used the |
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1442 next time the same script is imported. It will not be read again. |
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1443 *:import-cycle* |
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1444 The `import` commands are executed when encountered. If that script (directly |
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1445 or indirectly) imports the current script, then items defined after the |
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|
1446 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
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1447 result in undefined items. |
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1448 |
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1449 |
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1450 Import in an autoload script ~ |
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1451 |
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|
1452 For optimal startup speed, loading scripts should be postponed until they are |
19303 | 1453 actually needed. A recommended mechanism: |
19181
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1454 |
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1455 1. In the plugin define user commands, functions and/or mappings that refer to |
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1456 an autoload script. > |
23666 | 1457 command -nargs=1 SearchForStuff searchfor#Stuff(<f-args>) |
19181
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1458 |
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|
1459 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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1460 |
21825 | 1461 2. In the autoload script do the actual work. You can import items from |
19181
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1462 other files to split up functionality in appropriate pieces. > |
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|
1463 vim9script |
23573 | 1464 import FilterFunc from "../import/someother.vim" |
19181
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1465 def searchfor#Stuff(arg: string) |
22391
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1466 var filtered = FilterFunc(arg) |
19181
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1467 ... |
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1468 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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1469 must be exactly the same as the prefix for the function name, that is how |
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1470 Vim finds the file. |
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1471 |
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1472 3. Other functionality, possibly shared between plugins, contains the exported |
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1473 items and any private items. > |
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1474 vim9script |
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|
1475 var localVar = 'local' |
22171 | 1476 export def FilterFunc(arg: string): string |
19181
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1477 ... |
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1478 < This goes in .../import/someother.vim. |
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1479 |
21771
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|
1480 When compiling a `:def` function and a function in an autoload script is |
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|
1481 encountered, the script is not loaded until the `:def` function is called. |
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1482 |
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1483 |
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1484 Import in legacy Vim script ~ |
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1485 |
20856 | 1486 If an `import` statement is used in legacy Vim script, the script-local "s:" |
1487 namespace will be used for the imported item, even when "s:" is not specified. | |
19181
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1488 |
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1489 |
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1490 ============================================================================== |
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1491 |
22328 | 1492 6. Future work: classes *vim9-classes* |
1493 | |
1494 Above "class" was mentioned a few times, but it has not been implemented yet. | |
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1495 Most of Vim9 script can be created without this functionality, and since |
22328 | 1496 implementing classes is going to be a lot of work, it is left for the future. |
1497 For now we'll just make sure classes can be added later. | |
1498 | |
1499 Thoughts: | |
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|
1500 - `class` / `endclass`, the whole class must be in one file |
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|
1501 - Class names are always CamelCase (to avoid a name clash with builtin types) |
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1502 - A single constructor called "constructor" |
22328 | 1503 - Single inheritance with `class ThisClass extends BaseClass` |
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1504 - `abstract class` (class with incomplete implementation) |
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1505 - `interface` / `endinterface` (abstract class without any implementation) |
22328 | 1506 - `class SomeClass implements SomeInterface` |
1507 - Generics for class: `class <Tkey, Tentry>` | |
1508 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
1509 | |
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1510 Again, much of this is from TypeScript with a slightly different syntax. |
22328 | 1511 |
1512 Some things that look like good additions: | |
1513 - Use a class as an interface (like Dart) | |
1514 - Extend a class with methods, using an import (like Dart) | |
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1515 - Mixins |
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1516 - For testing: Mock mechanism |
22328 | 1517 |
1518 An important class that will be provided is "Promise". Since Vim is single | |
1519 threaded, connecting asynchronous operations is a natural way of allowing | |
1520 plugins to do their work without blocking the user. It's a uniform way to | |
1521 invoke callbacks and handle timeouts and errors. | |
1522 | |
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1523 Some examples: > |
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1524 |
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1525 abstract class Person |
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1526 static const prefix = 'xxx' |
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1527 var name: string |
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1528 |
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1529 def constructor(name: string) |
25402 | 1530 this.name = name |
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1531 enddef |
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1532 |
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1533 def display(): void |
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1534 echo name |
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1535 enddef |
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1536 |
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1537 abstract def find(string): Person |
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1538 endclass |
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1539 |
22328 | 1540 ============================================================================== |
1541 | |
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1542 9. Rationale *vim9-rationale* |
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1543 |
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1544 The :def command ~ |
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1545 |
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1546 Plugin writers have asked for much faster Vim script. Investigations have |
19303 | 1547 shown that keeping the existing semantics of function calls make this close to |
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1548 impossible, because of the overhead involved with calling a function, setting |
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1549 up the local function scope and executing lines. There are many details that |
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1550 need to be handled, such as error messages and exceptions. The need to create |
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1551 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1552 much overhead that cannot be avoided. |
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1553 |
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1554 Therefore the `:def` method to define a new-style function had to be added, |
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1555 which allows for a function with different semantics. Most things still work |
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1556 as before, but some parts do not. A new way to define a function was |
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1557 considered the best way to separate the legacy style code from Vim9 style code. |
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1558 |
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1559 Using "def" to define a function comes from Python. Other languages use |
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1560 "function" which clashes with legacy Vim script. |
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1561 |
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1562 |
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1563 Type checking ~ |
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1564 |
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1565 When compiling lines of Vim commands into instructions as much as possible |
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1566 should be done at compile time. Postponing it to runtime makes the execution |
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1567 slower and means mistakes are found only later. For example, when |
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1568 encountering the "+" character and compiling this into a generic add |
23666 | 1569 instruction, at runtime the instruction would have to inspect the type of the |
1570 arguments and decide what kind of addition to do. And when the type is | |
1571 dictionary throw an error. If the types are known to be numbers then an "add | |
1572 number" instruction can be used, which is faster. The error can be given at | |
1573 compile time, no error handling is needed at runtime, since adding two numbers | |
1574 cannot fail. | |
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1575 |
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1576 The syntax for types, using <type> for compound types, is similar to Java. It |
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1577 is easy to understand and widely used. The type names are what were used in |
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1578 Vim before, with some additions such as "void" and "bool". |
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1579 |
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1580 |
22328 | 1581 Removing clutter and weirdness ~ |
20856 | 1582 |
22328 | 1583 Once decided that `:def` functions have different syntax than legacy functions, |
1584 we are free to add improvements to make the code more familiar for users who | |
1585 know popular programming languages. In other words: remove weird things that | |
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1586 only Vim does. |
22328 | 1587 |
1588 We can also remove clutter, mainly things that were done to make Vim script | |
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1589 backwards compatible with the good old Vi commands. |
20856 | 1590 |
22328 | 1591 Examples: |
1592 - Drop `:call` for calling a function and `:eval` for manipulating data. | |
1593 - Drop using a leading backslash for line continuation, automatically figure | |
1594 out where an expression ends. | |
20856 | 1595 |
22328 | 1596 However, this does require that some things need to change: |
1597 - Comments start with # instead of ", to avoid confusing them with strings. | |
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1598 This is good anyway, it is known from several popular languages. |
22328 | 1599 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
1600 expressions (single quote can be a string or a mark, "/" can be divide or a | |
1601 search command, etc.). | |
1602 | |
1603 Goal is to limit the differences. A good criteria is that when the old syntax | |
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1604 is accidentally used you are very likely to get an error message. |
20856 | 1605 |
1606 | |
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1607 Syntax and semantics from popular languages ~ |
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1608 |
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1609 Script writers have complained that the Vim script syntax is unexpectedly |
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1610 different from what they are used to. To reduce this complaint popular |
20856 | 1611 languages are used as an example. At the same time, we do not want to abandon |
1612 the well-known parts of legacy Vim script. | |
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1613 |
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1614 For many things TypeScript is followed. It's a recent language that is |
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1615 gaining popularity and has similarities with Vim script. It also has a |
22328 | 1616 mix of static typing (a variable always has a known value type) and dynamic |
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1617 typing (a variable can have different types, this changes at runtime). Since |
22328 | 1618 legacy Vim script is dynamically typed and a lot of existing functionality |
1619 (esp. builtin functions) depends on that, while static typing allows for much | |
1620 faster execution, we need to have this mix in Vim9 script. | |
1621 | |
22171 | 1622 There is no intention to completely match TypeScript syntax and semantics. We |
1623 just want to take those parts that we can use for Vim and we expect Vim users | |
22328 | 1624 will be happy with. TypeScript is a complex language with its own history, |
1625 advantages and disadvantages. To get an idea of the disadvantages read the | |
1626 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
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1627 parts" and read the "Things to avoid" section. |
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1628 |
22328 | 1629 People familiar with other languages (Java, Python, etc.) will also find |
1630 things in TypeScript that they do not like or do not understand. We'll try to | |
1631 avoid those things. | |
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1632 |
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1633 Specific items from TypeScript we avoid: |
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1634 - Overloading "+", using it both for addition and string concatenation. This |
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1635 goes against legacy Vim script and often leads to mistakes. For that reason |
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1636 we will keep using ".." for string concatenation. Lua also uses ".." this |
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1637 way. And it allows for conversion to string for more values. |
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1638 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
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1639 cannot assign the value to a boolean. That is inconsistent and can be |
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1640 annoying. Vim recognizes an expression with && or || and allows using the |
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1641 result as a bool. TODO: to be reconsidered |
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1642 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
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1643 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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1644 Falsy. |
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1645 - TypeScript has various "Readonly" types, which have limited usefulness, |
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1646 since a type cast can remove the immutable nature. Vim locks the value, |
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1647 which is more flexible, but is only checked at runtime. |
22171 | 1648 |
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1649 |
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1650 Declarations ~ |
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1651 |
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1652 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
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1653 are used. That is different, thus it's good to use a different command: |
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1654 `:var`. This is used in many languages. The semantics might be slightly |
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1655 different, but it's easily recognized as a declaration. |
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1656 |
23047 | 1657 Using `:const` for constants is common, but the semantics varies. Some |
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1658 languages only make the variable immutable, others also make the value |
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1659 immutable. Since "final" is well known from Java for only making the variable |
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1660 immutable we decided to use that. And then `:const` can be used for making |
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1661 both immutable. This was also used in legacy Vim script and the meaning is |
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1662 almost the same. |
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1663 |
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1664 What we end up with is very similar to Dart: > |
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1665 :var name # mutable variable and value |
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1666 :final name # immutable variable, mutable value |
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1667 :const name # immutable variable and value |
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1668 |
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1669 Since legacy and Vim9 script will be mixed and global variables will be |
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1670 shared, optional type checking is desirable. Also, type inference will avoid |
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1671 the need for specifying the type in many cases. The TypeScript syntax fits |
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1672 best for adding types to declarations: > |
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1673 var name: string # string type is specified |
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1674 ... |
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1675 name = 'John' |
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1676 const greeting = 'hello' # string type is inferred |
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1677 |
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1678 This is how we put types in a declaration: > |
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1679 var mylist: list<string> |
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1680 final mylist: list<string> = ['foo'] |
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1681 def Func(arg1: number, arg2: string): bool |
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1682 |
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1683 Two alternatives were considered: |
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1684 1. Put the type before the name, like Dart: > |
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1685 var list<string> mylist |
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1686 final list<string> mylist = ['foo'] |
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1687 def Func(number arg1, string arg2) bool |
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1688 2. Put the type after the variable name, but do not use a colon, like Go: > |
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1689 var mylist list<string> |
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1690 final mylist list<string> = ['foo'] |
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1691 def Func(arg1 number, arg2 string) bool |
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1692 |
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1693 The first is more familiar for anyone used to C or Java. The second one |
22565 | 1694 doesn't really have an advantage over the first, so let's discard the second. |
22391
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1695 |
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1696 Since we use type inference the type can be left out when it can be inferred |
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1697 from the value. This means that after `var` we don't know if a type or a name |
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1698 follows. That makes parsing harder, not only for Vim but also for humans. |
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1699 Also, it will not be allowed to use a variable name that could be a type name, |
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1700 using `var string string` is too confusing. |
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1701 |
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1702 The chosen syntax, using a colon to separate the name from the type, adds |
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1703 punctuation, but it actually makes it easier to recognize the parts of a |
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1704 declaration. |
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1705 |
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1706 |
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1707 Expressions ~ |
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1708 |
22565 | 1709 Expression evaluation was already close to what other languages are doing. |
1710 Some details are unexpected and can be improved. For example a boolean | |
1711 condition would accept a string, convert it to a number and check if the | |
1712 number is non-zero. This is unexpected and often leads to mistakes, since | |
1713 text not starting with a number would be converted to zero, which is | |
22723 | 1714 considered false. Thus using a string for a condition would often not give an |
1715 error and be considered false. That is confusing. | |
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1716 |
23047 | 1717 In Vim9 type checking is stricter to avoid mistakes. Where a condition is |
22565 | 1718 used, e.g. with the `:if` command and the `||` operator, only boolean-like |
1719 values are accepted: | |
1720 true: `true`, `v:true`, `1`, `0 < 9` | |
1721 false: `false`, `v:false`, `0`, `0 > 9` | |
1722 Note that the number zero is false and the number one is true. This is more | |
22723 | 1723 permissive than most other languages. It was done because many builtin |
22565 | 1724 functions return these values. |
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1725 |
22565 | 1726 If you have any type of value and want to use it as a boolean, use the `!!` |
1727 operator: | |
24751 | 1728 true: `!!'text'`, `!![99]`, `!!{'x': 1}`, `!!99` |
22565 | 1729 false: `!!''`, `!![]`, `!!{}` |
1730 | |
1731 From a language like JavaScript we have this handy construct: > | |
1732 GetName() || 'unknown' | |
1733 However, this conflicts with only allowing a boolean for a condition. | |
1734 Therefore the "??" operator was added: > | |
1735 GetName() ?? 'unknown' | |
1736 Here you can explicitly express your intention to use the value as-is and not | |
1737 result in a boolean. This is called the |falsy-operator|. | |
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1738 |
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1739 |
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1740 Import and Export ~ |
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1741 |
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1742 A problem of legacy Vim script is that by default all functions and variables |
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1743 are global. It is possible to make them script-local, but then they are not |
22171 | 1744 available in other scripts. This defies the concept of a package that only |
1745 exports selected items and keeps the rest local. | |
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1746 |
21825 | 1747 In Vim9 script a mechanism very similar to the JavaScript import and export |
19181
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1748 mechanism is supported. It is a variant to the existing `:source` command |
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1749 that works like one would expect: |
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1750 - Instead of making everything global by default, everything is script-local, |
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1751 unless exported. |
22171 | 1752 - When importing a script the symbols that are imported are explicitly listed, |
1753 avoiding name conflicts and failures if functionality is added later. | |
19181
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1754 - The mechanism allows for writing a big, long script with a very clear API: |
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1755 the exported function(s) and class(es). |
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1756 - By using relative paths loading can be much faster for an import inside of a |
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1757 package, no need to search many directories. |
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1758 - Once an import has been used, it can be cached and loading it again can be |
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1759 avoided. |
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1760 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1761 |
20856 | 1762 When sourcing a Vim9 script from a legacy script, only the items defined |
1763 globally can be used, not the exported items. Alternatives considered: | |
1764 - All the exported items become available as script-local items. This makes | |
22171 | 1765 it uncontrollable what items get defined and likely soon leads to trouble. |
20856 | 1766 - Use the exported items and make them global. Disadvantage is that it's then |
1767 not possible to avoid name clashes in the global namespace. | |
1768 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
1769 makes it difficult to use scripts for testing, or sourcing them from the | |
1770 command line to try them out. | |
22171 | 1771 Note that you can also use `:import` in legacy Vim script, see above. |
20856 | 1772 |
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1773 |
22328 | 1774 Compiling functions early ~ |
1775 | |
1776 Functions are compiled when called or when `:defcompile` is used. Why not | |
1777 compile them early, so that syntax and type errors are reported early? | |
1778 | |
1779 The functions can't be compiled right away when encountered, because there may | |
1780 be forward references to functions defined later. Consider defining functions | |
1781 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
1782 to reorder the functions to avoid forward references. | |
1783 | |
1784 An alternative would be to first scan through the file to locate items and | |
1785 figure out their type, so that forward references are found, and only then | |
1786 execute the script and compile the functions. This means the script has to be | |
1787 parsed twice, which is slower, and some conditions at the script level, such | |
1788 as checking if a feature is supported, are hard to use. An attempt was made | |
1789 to see if it works, but it turned out to be impossible to make work nicely. | |
1790 | |
1791 It would be possible to compile all the functions at the end of the script. | |
1792 The drawback is that if a function never gets called, the overhead of | |
1793 compiling it counts anyway. Since startup speed is very important, in most | |
1794 cases it's better to do it later and accept that syntax and type errors are | |
1795 only reported then. In case these errors should be found early, e.g. when | |
1796 testing, the `:defcompile` command will help out. | |
1797 | |
1798 | |
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1799 Why not use an embedded language? ~ |
19181
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1800 |
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1801 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
22328 | 1802 these interfaces have never become widely used, for various reasons. When |
1803 Vim9 was designed a decision was made to make these interfaces lower priority | |
1804 and concentrate on Vim script. | |
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1805 |
22328 | 1806 Still, plugin writers may find other languages more familiar, want to use |
1807 existing libraries or see a performance benefit. We encourage plugin authors | |
1808 to write code in any language and run it as an external tool, using jobs and | |
1809 channels. We can try to make this easier somehow. | |
1810 | |
1811 Using an external tool also has disadvantages. An alternative is to convert | |
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1812 the tool into Vim script. For that to be possible without too much |
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1813 translation, and keeping the code fast at the same time, the constructs of the |
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1814 tool need to be supported. Since most languages support classes the lack of |
22171 | 1815 support for classes in Vim is then a problem. |
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1816 |
22328 | 1817 |
1818 Classes ~ | |
1819 | |
1820 Vim supports a kind-of object oriented programming by adding methods to a | |
1821 dictionary. With some care this can be made to work, but it does not look | |
1822 like real classes. On top of that, it's quite slow, because of the use of | |
1823 dictionaries. | |
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1824 |
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1825 The support of classes in Vim9 script is a "minimal common functionality" of |
22171 | 1826 class support in most languages. It works much like Java, which is the most |
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1827 popular programming language. |
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1828 |
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1829 |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
|
1830 |
94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
|
1831 vim:tw=78:ts=8:noet:ft=help:norl: |