Mercurial > vim
annotate runtime/doc/vim9.txt @ 24569:e3ec2ec8841a
Update runtime files
Commit: https://github.com/vim/vim/commit/4c295027a426986566cd7a76c47a6d3a529727e7
Author: Bram Moolenaar <Bram@vim.org>
Date: Sun May 2 17:19:11 2021 +0200
Update runtime files
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Sun, 02 May 2021 17:30:05 +0200 |
| parents | 3bfec39ce31c |
| children | e69e7133c9cf |
| rev | line source |
|---|---|
| 24569 | 1 *vim9.txt* For Vim version 8.2. Last change: 2021 Apr 28 |
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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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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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24 9. Rationale |vim9-rationale| |
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26 ============================================================================== |
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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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55 |
| 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') |
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104 - You cannot use `:xit`, `:t`, `:k`, `:append`, `:change`, `:insert`, `:open` |
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105 or curly-braces names. |
| 22441 | 106 - A range before a command must be prefixed with a colon: > |
| 23573 | 107 :%s/this/that |
| 108 - Unless mentioned specifically, the highest |scriptversion| is used. | |
| 22441 | 109 |
| 110 | |
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111 Comments starting with # ~ |
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112 |
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113 In legacy Vim script comments start with double quote. In Vim9 script |
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114 comments start with #. > |
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115 # declarations |
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116 var count = 0 # number of occurrences |
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118 The reason is that a double quote can also be the start of a string. In many |
| 21825 | 119 places, especially halfway through an expression with a line break, it's hard |
| 120 to tell what the meaning is, since both a string and a comment can be followed | |
| 121 by arbitrary text. To avoid confusion only # comments are recognized. This | |
| 122 is the same as in shell scripts and Python programs. | |
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123 |
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124 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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125 `:number` for that. > |
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126 101 number |
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127 |
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128 To improve readability there must be a space between a command and the # |
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129 that starts a comment: > |
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130 var name = value # comment |
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131 var name = value# error! |
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132 |
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133 Do not start a comment with #{, it looks like the legacy dictionary literal |
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134 and produces an error where this might be confusing. #{{ or #{{{ are OK, |
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135 these can be used to start a fold. |
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136 |
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137 In legacy Vim script # is also used for the alternate file name. In Vim9 |
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138 script you need to use %% instead. Instead of ## use %%% (stands for all |
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139 arguments). |
| 20115 | 140 |
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141 |
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142 Vim9 functions ~ |
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143 |
| 20241 | 144 A function defined with `:def` is compiled. Execution is many times faster, |
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145 often 10 to 100 times. |
| 20241 | 146 |
| 20552 | 147 Many errors are already found when compiling, before the function is executed. |
| 20241 | 148 The syntax is strict, to enforce code that is easy to read and understand. |
| 149 | |
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150 Compilation is done when any of these is encountered: |
| 23164 | 151 - the first time the function is called |
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152 - when the `:defcompile` command is encountered in the script after the |
| 21991 | 153 function was defined |
| 154 - `:disassemble` is used for the function. | |
| 155 - a function that is compiled calls the function or uses it as a function | |
| 156 reference | |
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157 *E1091* |
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158 If compilation fails it is not tried again on the next call, instead this |
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159 error is given: "E1091: Function is not compiled: {name}". |
| 24569 | 160 Compilation will fail when encountering a user command that has not been |
| 161 created yet. In this case you can call `execute()` to invoke it at runtime. > | |
| 162 def MyFunc() | |
| 163 execute('DefinedLater') | |
| 164 enddef | |
| 20552 | 165 |
| 166 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
| 23164 | 167 "closure". A `:def` function always aborts on an error (unless `:silent!` was |
| 168 used for the command or inside a `:try` block), does not get a range passed | |
| 23305 | 169 cannot be a "dict" function, and can always be a closure. |
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170 |
| 20241 | 171 The argument types and return type need to be specified. The "any" type can |
| 172 be used, type checking will then be done at runtime, like with legacy | |
| 173 functions. | |
| 174 | |
| 21825 | 175 Arguments are accessed by name, without "a:", just like any other language. |
| 176 There is no "a:" dictionary or "a:000" list. | |
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177 *vim9-variable-arguments* |
| 20241 | 178 Variable arguments are defined as the last argument, with a name and have a |
| 21825 | 179 list type, similar to TypeScript. For example, a list of numbers: > |
| 22171 | 180 def MyFunc(...itemlist: list<number>) |
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181 for item in itemlist |
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182 ... |
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183 |
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184 When a function argument is optional (it has a default value) passing `v:none` |
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185 as the argument results in using the default value. This is useful when you |
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186 want to specify a value for an argument that comes after an argument that |
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187 should use its default value. Example: > |
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188 def MyFunc(one = 'one', last = 'last) |
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189 ... |
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190 enddef |
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191 MyFunc(v:none, 'LAST') # first argument uses default value 'one' |
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192 < |
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193 *vim9-ignored-argument* |
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194 The argument "_" (an underscore) can be used to ignore the argument. This is |
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195 most useful in callbacks where you don't need it, but do need to give an |
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196 argument to match the call. E.g. when using map() two arguments are passed, |
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197 the key and the value, to ignore the key: > |
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198 map(myList, (_, v) => v * 2) |
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199 There is no error for using the "_" argument multiple times. No type needs to |
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200 be given. |
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201 |
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202 |
| 20241 | 203 Functions and variables are script-local by default ~ |
| 20856 | 204 *vim9-scopes* |
| 20115 | 205 When using `:function` or `:def` to specify a new function at the script level |
| 206 in a Vim9 script, the function is local to the script, as if "s:" was | |
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207 prefixed. Using the "s:" prefix is optional. To define a global function or |
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208 variable the "g:" prefix must be used. For functions in an autoload script |
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209 the "name#" prefix is sufficient. > |
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210 def ThisFunction() # script-local |
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211 def s:ThisFunction() # script-local |
| 22171 | 212 def g:ThatFunction() # global |
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213 def scriptname#function() # autoload |
| 20115 | 214 |
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215 When using `:function` or `:def` to specify a nested function inside a `:def` |
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216 function, this nested function is local to the code block it is defined in. |
| 22565 | 217 In a `:def` function it is not possible to define a script-local function. It |
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218 is possible to define a global function by using the "g:" prefix. |
| 20115 | 219 |
| 220 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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221 search for the function: |
| 22565 | 222 - in the function scope, in block scopes |
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223 - in the script scope, possibly imported |
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224 - in the list of global functions |
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225 However, it is recommended to always use "g:" to refer to a global function |
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226 for clarity. |
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227 |
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228 Since a script-local function reference can be used without "s:" the name must |
| 24278 | 229 start with an upper case letter even when using the "s:" prefix. In legacy |
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230 script "s:funcref" could be used, because it could not be referred to with |
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231 "funcref". In Vim9 script it can, therefore "s:Funcref" must be used to avoid |
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232 that the name interferes with builtin functions. |
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233 |
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234 In all cases the function must be defined before used. That is when it is |
| 22723 | 235 called, when `:defcompile` causes it to be compiled, or when code that calls |
| 236 it is being compiled (to figure out the return type). | |
| 20241 | 237 |
| 21676 | 238 The result is that functions and variables without a namespace can usually be |
| 20241 | 239 found in the script, either defined there or imported. Global functions and |
| 21676 | 240 variables could be defined anywhere (good luck finding out where!). |
| 20115 | 241 |
| 21825 | 242 Global functions can still be defined and deleted at nearly any time. In |
| 20317 | 243 Vim9 script script-local functions are defined once when the script is sourced |
| 20552 | 244 and cannot be deleted or replaced. |
| 20115 | 245 |
| 23305 | 246 When compiling a function and a function call is encountered for a function |
| 247 that is not (yet) defined, the |FuncUndefined| autocommand is not triggered. | |
| 248 You can use an autoload function if needed, or call a legacy function and have | |
| 249 |FuncUndefined| triggered there. | |
| 250 | |
| 20115 | 251 |
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252 Reloading a Vim9 script clears functions and variables by default ~ |
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253 *vim9-reload* |
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254 When loading a legacy Vim script a second time nothing is removed, the |
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255 commands will replace existing variables and functions and create new ones. |
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256 |
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257 When loading a Vim9 script a second time all existing script-local functions |
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258 and variables are deleted, thus you start with a clean slate. This is useful |
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259 if you are developing a plugin and want to try a new version. If you renamed |
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260 something you don't have to worry about the old name still hanging around. |
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261 |
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262 If you do want to keep items, use: > |
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263 vim9script noclear |
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264 |
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265 You want to use this in scripts that use a `finish` command to bail out at |
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266 some point when loaded again. E.g. when a buffer local option is set: > |
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267 vim9script noclear |
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268 setlocal completefunc=SomeFunc |
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269 if exists('*g:SomeFunc') | finish | endif |
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270 def g:SomeFunc() |
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271 .... |
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272 |
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273 |
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274 Variable declarations with :var, :final and :const ~ |
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275 *vim9-declaration* *:var* |
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276 Local variables need to be declared with `:var`. Local constants need to be |
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277 declared with `:final` or `:const`. We refer to both as "variables" in this |
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278 section. |
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279 |
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280 Variables can be local to a script, function or code block: > |
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281 vim9script |
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282 var script_var = 123 |
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283 def SomeFunc() |
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284 var func_var = script_var |
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285 if cond |
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286 var block_var = func_var |
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287 ... |
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288 |
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289 The variables are only visible in the block where they are defined and nested |
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290 blocks. Once the block ends the variable is no longer accessible: > |
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291 if cond |
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292 var inner = 5 |
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293 else |
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294 var inner = 0 |
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295 endif |
| 22171 | 296 echo inner # Error! |
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297 |
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298 The declaration must be done earlier: > |
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299 var inner: number |
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300 if cond |
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301 inner = 5 |
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302 else |
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303 inner = 0 |
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304 endif |
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305 echo inner |
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306 |
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307 To intentionally hide a variable from code that follows, a block can be |
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308 used: > |
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309 { |
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310 var temp = 'temp' |
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311 ... |
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312 } |
| 22171 | 313 echo temp # Error! |
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314 |
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315 Declaring a variable with a type but without an initializer will initialize to |
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316 zero, false or empty. |
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317 |
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318 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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319 without any command. The same for global, window, tab, buffer and Vim |
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320 variables, because they are not really declared. They can also be deleted |
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321 with `:unlet`. |
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322 |
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323 `:lockvar` does not work on local variables. Use `:const` and `:final` |
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324 instead. |
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325 |
| 24024 | 326 Variables, functions and function arguments cannot shadow previously defined |
| 327 or imported variables and functions in the same script file. | |
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328 Variables may shadow Ex commands, rename the variable if needed. |
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329 |
| 24387 | 330 Global variables must be prefixed with "g:", also at the script level. > |
| 19968 | 331 vim9script |
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332 var script_local = 'text' |
| 21499 | 333 g:global = 'value' |
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334 var Funcref = g:ThatFunction |
| 19968 | 335 |
| 24387 | 336 Global functions must be prefixed with "g:" when defining them, but can be |
| 337 called without "g:". > | |
| 338 vim9script | |
| 339 def g:GlobalFunc(): string | |
| 340 return 'text' | |
| 341 enddef | |
| 342 echo GlobalFunc() | |
| 343 The "g:" prefix is not needed for auto-load functions. | |
| 344 | |
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345 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
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346 used to repeat a `:substitute` command. |
| 24468 | 347 *vim9-unpack-ignore* |
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348 For an unpack assignment the underscore can be used to ignore a list item, |
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349 similar to how a function argument can be ignored: > |
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350 [a, _, c] = theList |
| 24468 | 351 To ignore any remaining items: > |
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352 [a, b; _] = longList |
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353 |
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354 < *E1092* |
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355 Declaring more than one variable at a time, using the unpack notation, is |
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356 currently not supported: > |
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357 var [v1, v2] = GetValues() # Error! |
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358 That is because the type needs to be inferred from the list item type, which |
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359 isn't that easy. |
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360 |
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361 |
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362 Constants ~ |
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363 *vim9-const* *vim9-final* |
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364 How constants work varies between languages. Some consider a variable that |
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365 can't be assigned another value a constant. JavaScript is an example. Others |
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366 also make the value immutable, thus when a constant uses a list, the list |
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367 cannot be changed. In Vim9 we can use both. |
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368 |
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369 `:const` is used for making both the variable and the value a constant. Use |
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370 this for composite structures that you want to make sure will not be modified. |
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371 Example: > |
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372 const myList = [1, 2] |
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373 myList = [3, 4] # Error! |
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374 myList[0] = 9 # Error! |
| 24024 | 375 myList->add(3) # Error! |
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376 < *:final* |
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377 `:final` is used for making only the variable a constant, the value can be |
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378 changed. This is well known from Java. Example: > |
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379 final myList = [1, 2] |
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380 myList = [3, 4] # Error! |
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381 myList[0] = 9 # OK |
| 24024 | 382 myList->add(3) # OK |
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383 |
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384 It is common to write constants as ALL_CAPS, but you don't have to. |
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385 |
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386 The constant only applies to the value itself, not what it refers to. > |
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387 final females = ["Mary"] |
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388 const NAMES = [["John", "Peter"], females] |
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389 NAMES[0] = ["Jack"] # Error! |
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390 NAMES[0][0] = "Jack" # Error! |
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391 NAMES[1] = ["Emma"] # Error! |
| 23573 | 392 NAMES[1][0] = "Emma" # OK, now females[0] == "Emma" |
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393 |
|
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394 |
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395 Omitting :call and :eval ~ |
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396 |
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397 Functions can be called without `:call`: > |
| 22171 | 398 writefile(lines, 'file') |
| 19303 | 399 Using `:call` is still possible, but this is discouraged. |
|
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400 |
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401 A method call without `eval` is possible, so long as the start is an |
|
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402 identifier or can't be an Ex command. For a function either "(" or "->" must |
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403 be following, without a line break. Examples: > |
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404 myList->add(123) |
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405 g:myList->add(123) |
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406 [1, 2, 3]->Process() |
|
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407 {a: 1, b: 2}->Process() |
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408 "foobar"->Process() |
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409 ("foobar")->Process() |
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410 'foobar'->Process() |
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411 ('foobar')->Process() |
|
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412 |
| 21825 | 413 In the rare case there is ambiguity between a function name and an Ex command, |
| 21676 | 414 prepend ":" to make clear you want to use the Ex command. For example, there |
| 415 is both the `:substitute` command and the `substitute()` function. When the | |
| 416 line starts with `substitute(` this will use the function. Prepend a colon to | |
| 417 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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|
418 :substitute(pattern (replacement ( |
|
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patch 8.2.0294: cannot use Ex command that is also a function name
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419 |
|
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420 Note that while variables need to be defined before they can be used, |
| 21825 | 421 functions can be called before being defined. This is required to allow |
| 422 for cyclic dependencies between functions. It is slightly less efficient, | |
|
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423 since the function has to be looked up by name. And a typo in the function |
|
21516
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424 name will only be found when the function is called. |
|
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425 |
|
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426 |
| 19968 | 427 Omitting function() ~ |
| 428 | |
| 429 A user defined function can be used as a function reference in an expression | |
| 430 without `function()`. The argument types and return type will then be checked. | |
| 431 The function must already have been defined. > | |
| 432 | |
|
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433 var Funcref = MyFunction |
| 19968 | 434 |
| 435 When using `function()` the resulting type is "func", a function with any | |
| 436 number of arguments and any return type. The function can be defined later. | |
| 437 | |
| 438 | |
|
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|
439 Lambda using => instead of -> ~ |
| 24387 | 440 *vim9-lambda* |
|
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|
441 In legacy script there can be confusion between using "->" for a method call |
|
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442 and for a lambda. Also, when a "{" is found the parser needs to figure out if |
|
c76240efdf02
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443 it is the start of a lambda or a dictionary, which is now more complicated |
|
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444 because of the use of argument types. |
|
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|
445 |
|
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446 To avoid these problems Vim9 script uses a different syntax for a lambda, |
|
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447 which is similar to Javascript: > |
|
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448 var Lambda = (arg) => expression |
|
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449 |
|
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450 No line break is allowed in the arguments of a lambda up to and including the |
|
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|
451 "=>". This is OK: > |
|
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452 filter(list, (k, v) => |
|
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453 v > 0) |
|
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454 This does not work: > |
|
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455 filter(list, (k, v) |
|
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456 => v > 0) |
|
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457 This also does not work: > |
|
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458 filter(list, (k, |
|
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459 v) => v > 0) |
|
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|
460 But you can use a backslash to concatenate the lines before parsing: > |
|
517fca70e084
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|
461 filter(list, (k, |
|
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462 \ v) |
|
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463 \ => v > 0) |
|
24408
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patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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|
464 < *vim9-lambda-arguments* |
|
96e0b898d5b4
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|
465 In legacy script a lambda could be called with any number of extra arguments, |
|
96e0b898d5b4
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466 there was no way to warn for not using them. In Vim9 script the number of |
|
96e0b898d5b4
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|
467 arguments must match. If you do want to accept any arguments, or any further |
|
96e0b898d5b4
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|
468 arguments, use "..._", which makes the function accept |
|
96e0b898d5b4
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|
469 |vim9-variable-arguments|. Example: > |
|
96e0b898d5b4
patch 8.2.2744: Vim9: no way to explicitly ignore an argument
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470 var Callback = (..._) => 'anything' |
|
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471 echo Callback(1, 2, 3) # displays "anything" |
|
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472 |
| 24387 | 473 < *inline-function* |
|
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474 Additionally, a lambda can contain statements in {}: > |
|
c76240efdf02
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|
475 var Lambda = (arg) => { |
|
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476 g:was_called = 'yes' |
|
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477 return expression |
|
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|
478 } |
| 24387 | 479 This can be useful for a timer, for example: > |
| 480 var count = 0 | |
| 481 var timer = timer_start(500, (_) => { | |
| 482 count += 1 | |
| 483 echom 'Handler called ' .. count | |
| 484 }, {repeat: 3}) | |
| 485 | |
|
24272
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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|
486 |
|
cabed216cc2f
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|
487 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
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|
488 characters, e.g.: > |
|
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
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|
489 var d = mapnew(dict, (k, v): string => { |
|
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|
490 return 'value' |
|
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491 }) |
|
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|
492 No command can follow the "{", only a comment can be used there. |
|
cabed216cc2f
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|
493 |
|
cabed216cc2f
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|
494 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
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|
495 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
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|
496 "{". Unfortunately this means using "() => { command }" does not work, line |
|
cabed216cc2f
patch 8.2.2677: Vim9: cannot use only some of the default arguments
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|
497 breaks are always required. |
|
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|
498 |
| 23737 | 499 *vim9-curly* |
|
23358
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patch 8.2.2222: Vim9: cannot keep script variables when reloading
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changeset
|
500 To avoid the "{" of a dictionary literal to be recognized as a statement block |
| 24024 | 501 wrap it in parentheses: > |
|
23358
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|
502 var Lambda = (arg) => ({key: 42}) |
|
23318
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|
503 |
| 23737 | 504 Also when confused with the start of a command block: > |
| 505 ({ | |
| 506 key: value | |
| 507 })->method() | |
| 508 | |
|
23318
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changeset
|
509 |
|
19999
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
Bram Moolenaar <Bram@vim.org>
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changeset
|
510 Automatic line continuation ~ |
|
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
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|
511 |
|
844c7646f61b
patch 8.2.0555: Vim9: line continuation is not always needed
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changeset
|
512 In many cases it is obvious that an expression continues on the next line. In |
|
23392
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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changeset
|
513 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
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changeset
|
514 |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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|
515 var mylist = [ |
|
19999
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patch 8.2.0555: Vim9: line continuation is not always needed
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|
516 'one', |
|
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patch 8.2.0555: Vim9: line continuation is not always needed
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517 'two', |
|
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patch 8.2.0555: Vim9: line continuation is not always needed
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518 ] |
|
20011
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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|
519 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>
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|
520 var mydict = { |
|
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
521 one: 1, |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
522 two: 2, |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
523 } |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
524 Function call: > |
|
22391
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|
525 var result = Func( |
|
20011
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patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
526 arg1, |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
527 arg2 |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
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|
528 ) |
|
628011800942
patch 8.2.0561: Vim9: cannot split function call in multiple lines
Bram Moolenaar <Bram@vim.org>
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|
529 |
|
20982
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
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changeset
|
530 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
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|
531 possible just before or after the operator. For example: > |
|
22391
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|
532 var text = lead |
|
20982
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patch 8.2.1042: Vim9: cannot put an operator on the next line
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|
533 .. middle |
|
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
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|
534 .. end |
|
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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changeset
|
535 var total = start + |
| 23573 | 536 end - |
|
20013
bf377a9ffccb
patch 8.2.0562: Vim9: cannot split an expression into multiple lines
Bram Moolenaar <Bram@vim.org>
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changeset
|
537 correction |
|
22391
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patch 8.2.1744: Vim9: using ":const!" is weird
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|
538 var result = positive |
|
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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|
539 ? PosFunc(arg) |
|
bb49b5090a9c
patch 8.2.1042: Vim9: cannot put an operator on the next line
Bram Moolenaar <Bram@vim.org>
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changeset
|
540 : 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
|
541 |
| 21499 | 542 For a method call using "->" and a member using a dot, a line break is allowed |
| 543 before it: > | |
|
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544 var result = GetBuilder() |
| 20965 | 545 ->BuilderSetWidth(333) |
| 546 ->BuilderSetHeight(777) | |
| 547 ->BuilderBuild() | |
|
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548 var result = MyDict |
| 21499 | 549 .member |
| 20965 | 550 |
|
23392
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
551 For commands that have an argument that is a list of commands, the | character |
|
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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552 at the start of the line indicates line continuation: > |
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patch 8.2.2239: Vim9: concatenating lines with backslash is inconvenient
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|
553 autocmd BufNewFile *.match if condition |
|
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554 | echo 'match' |
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555 | endif |
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556 |
|
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patch 8.2.1042: Vim9: cannot put an operator on the next line
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|
557 < *E1050* |
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558 To make it possible for the operator at the start of the line to be |
| 21250 | 559 recognized, it is required to put a colon before a range. This will add |
|
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560 "start" and print: > |
|
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561 var result = start |
|
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|
562 + print |
| 21250 | 563 Like this: > |
|
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564 var result = start + print |
| 21250 | 565 |
|
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|
566 This will assign "start" and print a line: > |
|
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567 var result = start |
|
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|
568 :+ print |
|
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569 |
| 23047 | 570 Note that the colon is not required for the |+cmd| argument: > |
| 571 edit +6 fname | |
| 572 | |
|
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patch 8.2.0563: Vim9: cannot split a function line
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573 It is also possible to split a function header over multiple lines, in between |
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574 arguments: > |
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575 def MyFunc( |
|
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576 text: string, |
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577 separator = '-' |
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578 ): string |
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579 |
| 23305 | 580 Since a continuation line cannot be easily recognized the parsing of commands |
|
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changeset
|
581 has been made stricter. E.g., because of the error in the first line, the |
| 23305 | 582 second line is seen as a separate command: > |
| 583 popup_create(some invalid expression, { | |
| 584 exit_cb: Func}) | |
| 585 Now "exit_cb: Func})" is actually a valid command: save any changes to the | |
| 586 file "_cb: Func})" and exit. To avoid this kind of mistake in Vim9 script | |
| 587 there must be white space between most command names and the argument. | |
| 588 | |
| 23666 | 589 However, the argument of a command that is a command won't be recognized. For |
| 590 example, after "windo echo expr" a line break inside "expr" will not be seen. | |
| 591 | |
| 23305 | 592 |
| 21250 | 593 Notes: |
| 594 - "enddef" cannot be used at the start of a continuation line, it ends the | |
| 595 current function. | |
| 596 - No line break is allowed in the LHS of an assignment. Specifically when | |
| 597 unpacking a list |:let-unpack|. This is OK: > | |
| 22171 | 598 [var1, var2] = |
| 21250 | 599 Func() |
| 600 < This does not work: > | |
| 22171 | 601 [var1, |
| 21250 | 602 var2] = |
| 603 Func() | |
| 604 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
| 605 similar commands. This is OK: > | |
| 22171 | 606 echo [1, |
| 21250 | 607 2] [3, |
| 608 4] | |
| 609 < This does not work: > | |
| 22171 | 610 echo [1, 2] |
| 21250 | 611 [3, 4] |
|
19999
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612 |
| 24569 | 613 |
| 614 White space ~ | |
| 615 | |
| 616 Vim9 script enforces proper use of white space. This is no longer allowed: > | |
| 617 var name=234 # Error! | |
| 618 var name= 234 # Error! | |
| 619 var name =234 # Error! | |
| 620 There must be white space before and after the "=": > | |
| 621 var name = 234 # OK | |
| 622 White space must also be put before the # that starts a comment after a | |
| 623 command: > | |
| 624 var name = 234# Error! | |
| 625 var name = 234 # OK | |
| 626 | |
| 627 White space is required around most operators. | |
| 628 | |
| 629 White space is required in a sublist (list slice) around the ":", except at | |
| 630 the start and end: > | |
| 631 otherlist = mylist[v : count] # v:count has a different meaning | |
| 632 otherlist = mylist[:] # make a copy of the List | |
| 633 otherlist = mylist[v :] | |
| 634 otherlist = mylist[: v] | |
| 635 | |
| 636 White space is not allowed: | |
| 637 - Between a function name and the "(": > | |
| 638 Func (arg) # Error! | |
| 639 Func | |
| 640 \ (arg) # Error! | |
| 641 Func | |
| 642 (arg) # Error! | |
| 643 Func(arg) # OK | |
| 644 Func( | |
| 645 arg) # OK | |
| 646 Func( | |
| 647 arg # OK | |
| 648 ) | |
| 649 | |
| 650 | |
|
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651 No curly braces expansion ~ |
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652 |
|
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653 |curly-braces-names| cannot be used. |
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654 |
|
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changeset
|
655 |
|
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656 Dictionary literals ~ |
|
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657 |
|
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658 Traditionally Vim has supported dictionary literals with a {} syntax: > |
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659 let dict = {'key': value} |
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|
660 |
|
23088
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661 Later it became clear that using a simple text key is very common, thus |
|
285cde4b8d0e
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662 literal dictionaries were introduced in a backwards compatible way: > |
|
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663 let dict = #{key: value} |
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664 |
|
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665 However, this #{} syntax is unlike any existing language. As it turns out |
|
285cde4b8d0e
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|
666 that using a literal key is much more common than using an expression, and |
|
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|
667 considering that JavaScript uses this syntax, using the {} form for dictionary |
|
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668 literals is considered a much more useful syntax. In Vim9 script the {} form |
|
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|
669 uses literal keys: > |
| 23666 | 670 var dict = {key: value} |
|
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|
671 |
|
23088
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|
672 This works for alphanumeric characters, underscore and dash. If you want to |
|
285cde4b8d0e
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|
673 use another character, use a single or double quoted string: > |
| 23666 | 674 var dict = {'key with space': value} |
| 675 var dict = {"key\twith\ttabs": value} | |
| 676 var dict = {'': value} # empty key | |
|
23088
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|
677 |
|
285cde4b8d0e
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|
678 In case the key needs to be an expression, square brackets can be used, just |
|
285cde4b8d0e
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|
679 like in JavaScript: > |
| 23666 | 680 var dict = {["key" .. nr]: value} |
|
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|
681 |
|
23827
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
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|
682 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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|
683 error. A number can be given with and without the []: > |
|
7e0d8f1cae7d
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Bram Moolenaar <Bram@vim.org>
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changeset
|
684 var dict = {123: 'without', [456]: 'with'} |
|
7e0d8f1cae7d
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Bram Moolenaar <Bram@vim.org>
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changeset
|
685 echo dict |
|
7e0d8f1cae7d
patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
parents:
23737
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changeset
|
686 {'456': 'with', '123': 'without'} |
|
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patch 8.2.2455: Vim9: key type for literal dict and indexing is inconsistent
Bram Moolenaar <Bram@vim.org>
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changeset
|
687 |
|
22936
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Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
688 |
|
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
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changeset
|
689 No :xit, :t, :k, :append, :change or :insert ~ |
| 19303 | 690 |
|
21584
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
Bram Moolenaar <Bram@vim.org>
parents:
21550
diff
changeset
|
691 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
|
692 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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21550
diff
changeset
|
693 Instead of `:t` you can use `:copy`. |
|
23978
54b2aa1f0d42
patch 8.2.2531: Vim9: the :k command is obscure
Bram Moolenaar <Bram@vim.org>
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23974
diff
changeset
|
694 Instead of `:k` you can use `:mark`. |
|
19181
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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changeset
|
695 |
| 19303 | 696 |
| 697 Comparators ~ | |
| 698 | |
| 699 The 'ignorecase' option is not used for comparators that use strings. | |
|
19181
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changeset
|
700 |
|
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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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changeset
|
701 |
| 24569 | 702 Abort after error ~ |
| 703 | |
| 704 In legacy script, when an error is encountered, Vim continues to execute | |
| 705 following lines. This can lead to a long sequence of errors and need to type | |
| 706 CTRL-C to stop it. In Vim9 script execution of commands stops at the first | |
| 707 error. Example: > | |
| 708 vim9script | |
| 709 var x = does-not-exist | |
| 710 echo 'not executed' | |
| 711 | |
| 712 | |
| 23666 | 713 For loop ~ |
| 714 | |
| 715 Legacy Vim script has some tricks to make a for loop over a list handle | |
| 716 deleting items at the current or previous item. In Vim9 script it just uses | |
| 717 the index, if items are deleted then items in the list will be skipped. | |
| 718 Example legacy script: > | |
| 719 let l = [1, 2, 3, 4] | |
| 720 for i in l | |
| 721 echo i | |
| 722 call remove(l, index(l, i)) | |
| 723 endfor | |
| 724 Would echo: | |
| 725 1 | |
| 726 2 | |
| 727 3 | |
| 728 4 | |
| 729 In compiled Vim9 script you get: | |
| 730 1 | |
| 731 3 | |
| 732 Generally, you should not change the list that is iterated over. Make a copy | |
| 733 first if needed. | |
| 734 | |
| 735 | |
|
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
736 Conditions and expressions ~ |
|
94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
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changeset
|
737 |
|
22500
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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changeset
|
738 Conditions and expressions are mostly working like they do in other languages. |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
739 Some values are different from legacy Vim script: |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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diff
changeset
|
740 value legacy Vim script Vim9 script ~ |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
741 0 falsy falsy |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
742 1 truthy truthy |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
743 99 truthy Error! |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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|
744 "0" falsy Error! |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
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changeset
|
745 "99" truthy Error! |
|
ef8a3177edc1
patch 8.2.1798: Vim9: trinary operator condition is too permissive
Bram Moolenaar <Bram@vim.org>
parents:
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diff
changeset
|
746 "text" falsy Error! |
|
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|
747 |
|
22500
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|
748 For the "??" operator and when using "!" then there is no error, every value |
|
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|
749 is either falsy or truthy. This is mostly like JavaScript, except that an |
|
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patch 8.2.1798: Vim9: trinary operator condition is too permissive
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|
750 empty list and dict is falsy: |
|
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|
751 |
|
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|
752 type truthy when ~ |
| 23466 | 753 bool true, v:true or 1 |
|
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|
754 number non-zero |
|
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755 float non-zero |
|
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756 string non-empty |
|
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|
757 blob non-empty |
|
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|
758 list non-empty (different from JavaScript) |
|
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|
759 dictionary non-empty (different from JavaScript) |
| 19968 | 760 func when there is a function name |
| 23466 | 761 special true or v:true |
|
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|
762 job when not NULL |
|
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|
763 channel when not NULL |
|
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|
764 class when not NULL |
| 23466 | 765 object when not NULL (TODO: when isTrue() returns true) |
|
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766 |
|
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patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
767 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
|
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|
768 one: > |
|
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|
769 1 || false == true |
|
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|
770 0 || 1 == true |
|
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|
771 0 || false == false |
|
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|
772 1 && true == true |
|
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|
773 0 && 1 == false |
|
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|
774 8 || 0 Error! |
|
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|
775 'yes' && 0 Error! |
|
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|
776 [] || 99 Error! |
|
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777 |
|
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|
778 When using "!" for inverting, there is no error for using any type and the |
|
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|
779 result is a boolean. "!!" can be used to turn any value into boolean: > |
| 23573 | 780 !'yes' == false |
|
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|
781 !![] == false |
| 23573 | 782 !![1, 2, 3] == true |
|
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|
783 |
|
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|
784 When using "`.."` for string concatenation arguments of simple types are |
|
22500
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|
785 always converted to string: > |
|
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|
786 'hello ' .. 123 == 'hello 123' |
| 23466 | 787 'hello ' .. v:true == 'hello true' |
|
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|
788 |
|
21771
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patch 8.2.1435: Vim9: always converting to string for ".." leads to mistakes
Bram Moolenaar <Bram@vim.org>
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changeset
|
789 Simple types are string, float, special and bool. For other types |string()| |
|
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|
790 can be used. |
|
23497
2247a2ce3630
patch 8.2.2291: Vim9: cannot use "null" for v:null
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|
791 *false* *true* *null* |
|
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|
792 In Vim9 script one can use "true" for v:true, "false" for v:false and "null" |
|
2247a2ce3630
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|
793 for v:null. When converting a boolean to a string "false" and "true" are |
|
2247a2ce3630
patch 8.2.2291: Vim9: cannot use "null" for v:null
Bram Moolenaar <Bram@vim.org>
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|
794 used, not "v:false" and "v:true" like in legacy script. "v:none" is not |
|
2247a2ce3630
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|
795 changed, it is only used in JSON and has no equivalent in other languages. |
|
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|
796 |
|
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patch 8.2.2605: Vim9: string index and slice does not include composing chars
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changeset
|
797 Indexing a string with [idx] or taking a slice with [idx : idx] uses character |
|
fcbb1d4df15b
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|
798 indexes instead of byte indexes. Composing characters are included. |
|
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changeset
|
799 Example: > |
| 21825 | 800 echo 'bár'[1] |
| 801 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
| 802 script this results in the string 'á'. | |
| 23573 | 803 A negative index is counting from the end, "[-1]" is the last character. |
| 23666 | 804 To exclude the last character use |slice()|. |
|
24272
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patch 8.2.2677: Vim9: cannot use only some of the default arguments
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diff
changeset
|
805 To count composing characters separately use |strcharpart()|. |
| 23573 | 806 If the index is out of range then an empty string results. |
| 807 | |
| 808 In legacy script "++var" and "--var" would be silently accepted and have no | |
| 809 effect. This is an error in Vim9 script. | |
| 810 | |
| 811 Numbers starting with zero are not considered to be octal, only numbers | |
| 812 starting with "0o" are octal: "0o744". |scriptversion-4| | |
| 21825 | 813 |
|
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|
814 |
| 21093 | 815 What to watch out for ~ |
| 816 *vim9-gotchas* | |
| 817 Vim9 was designed to be closer to often used programming languages, but at the | |
| 818 same time tries to support the legacy Vim commands. Some compromises had to | |
| 819 be made. Here is a summary of what might be unexpected. | |
| 820 | |
| 821 Ex command ranges need to be prefixed with a colon. > | |
| 23666 | 822 -> legacy Vim: shifts the previous line to the right |
| 823 ->func() Vim9: method call in a continuation line | |
| 824 :-> Vim9: shifts the previous line to the right | |
| 21093 | 825 |
| 23666 | 826 %s/a/b legacy Vim: substitute on all lines |
| 21093 | 827 x = alongname |
| 23666 | 828 % another Vim9: modulo operator in a continuation line |
| 829 :%s/a/b Vim9: substitute on all lines | |
| 830 't legacy Vim: jump to mark t | |
| 831 'text'->func() Vim9: method call | |
| 832 :'t Vim9: jump to mark t | |
| 21093 | 833 |
| 21676 | 834 Some Ex commands can be confused with assignments in Vim9 script: > |
| 23666 | 835 g:name = value # assignment |
| 836 g:pattern:cmd # invalid command - ERROR | |
| 837 :g:pattern:cmd # :global command | |
| 21676 | 838 |
| 21093 | 839 Functions defined with `:def` compile the whole function. Legacy functions |
| 840 can bail out, and the following lines are not parsed: > | |
| 841 func Maybe() | |
| 842 if !has('feature') | |
| 843 return | |
| 844 endif | |
| 845 use-feature | |
| 846 endfunc | |
| 847 Vim9 functions are compiled as a whole: > | |
| 848 def Maybe() | |
| 849 if !has('feature') | |
| 850 return | |
| 851 endif | |
| 23573 | 852 use-feature # May give a compilation error |
| 21093 | 853 enddef |
| 854 For a workaround, split it in two functions: > | |
| 855 func Maybe() | |
| 856 if has('feature') | |
| 23666 | 857 call MaybeInner() |
| 21093 | 858 endif |
| 859 endfunc | |
| 860 if has('feature') | |
| 861 def MaybeInner() | |
| 862 use-feature | |
| 863 enddef | |
| 864 endif | |
| 22171 | 865 Or put the unsupported code inside an `if` with a constant expression that |
| 21991 | 866 evaluates to false: > |
| 867 def Maybe() | |
| 868 if has('feature') | |
| 869 use-feature | |
| 870 endif | |
| 871 enddef | |
| 23573 | 872 < *vim9-user-command* |
| 23666 | 873 Another side effect of compiling a function is that the presence of a user |
| 23573 | 874 command is checked at compile time. If the user command is defined later an |
| 875 error will result. This works: > | |
| 876 command -nargs=1 MyCommand echom <q-args> | |
| 877 def Works() | |
| 878 MyCommand 123 | |
| 879 enddef | |
| 880 This will give an error for "MyCommand" not being defined: > | |
| 881 def Works() | |
| 882 command -nargs=1 MyCommand echom <q-args> | |
| 883 MyCommand 123 | |
| 884 enddef | |
| 885 A workaround is to invoke the command indirectly with `:execute`: > | |
| 886 def Works() | |
| 887 command -nargs=1 MyCommand echom <q-args> | |
| 888 execute 'MyCommand 123' | |
| 889 enddef | |
| 890 | |
| 21991 | 891 Note that for unrecognized commands there is no check for "|" and a following |
| 892 command. This will give an error for missing `endif`: > | |
| 893 def Maybe() | |
| 894 if has('feature') | use-feature | endif | |
| 895 enddef | |
| 21093 | 896 |
| 23305 | 897 Other differences ~ |
| 898 | |
| 899 Patterns are used like 'magic' is set, unless explicitly overruled. | |
| 900 The 'edcompatible' option value is not used. | |
| 901 The 'gdefault' option value is not used. | |
| 902 | |
| 24387 | 903 You may also find this wiki useful. It was written by an early adopter of |
| 24103 | 904 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
| 23305 | 905 |
|
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|
906 ============================================================================== |
|
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|
907 |
|
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
908 3. New style functions *fast-functions* |
|
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|
909 |
|
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|
910 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
|
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|
911 |
|
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|
912 *:def* |
| 21825 | 913 :def[!] {name}([arguments])[: {return-type}] |
|
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|
914 Define a new function by the name {name}. The body of |
|
94eda51ba9ba
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|
915 the function follows in the next lines, until the |
|
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|
916 matching `:enddef`. |
|
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|
917 |
|
19904
bd4f91762d0f
patch 8.2.0508: Vim9: func and partial types not done yet
Bram Moolenaar <Bram@vim.org>
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19646
diff
changeset
|
918 When {return-type} is omitted or is "void" the |
|
bd4f91762d0f
patch 8.2.0508: Vim9: func and partial types not done yet
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|
919 function is not expected to return anything. |
|
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|
920 |
|
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
921 {arguments} is a sequence of zero or more argument |
|
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|
922 declarations. There are three forms: |
|
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|
923 {name}: {type} |
|
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|
924 {name} = {value} |
|
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|
925 {name}: {type} = {value} |
|
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|
926 The first form is a mandatory argument, the caller |
|
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|
927 must always provide them. |
|
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|
928 The second and third form are optional arguments. |
|
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|
929 When the caller omits an argument the {value} is used. |
|
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|
930 |
| 20856 | 931 The function will be compiled into instructions when |
| 21499 | 932 called, or when `:disassemble` or `:defcompile` is |
| 933 used. Syntax and type errors will be produced at that | |
| 934 time. | |
| 20856 | 935 |
| 21499 | 936 It is possible to nest `:def` inside another `:def` or |
| 937 `:function` up to about 50 levels deep. | |
| 19303 | 938 |
|
22391
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Bram Moolenaar <Bram@vim.org>
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|
939 [!] is used as with `:function`. Note that |
|
a9fb7efa31d6
patch 8.2.1744: Vim9: using ":const!" is weird
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|
940 script-local functions cannot be deleted or redefined |
|
a9fb7efa31d6
patch 8.2.1744: Vim9: using ":const!" is weird
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|
941 later in Vim9 script. They can only be removed by |
|
a9fb7efa31d6
patch 8.2.1744: Vim9: using ":const!" is weird
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|
942 reloading the same script. |
|
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943 |
|
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|
944 *:enddef* |
| 21499 | 945 :enddef End of a function defined with `:def`. It should be on |
| 946 a line by its own. | |
|
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947 |
| 24387 | 948 You may also find this wiki useful. It was written by an early adopter of |
|
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|
949 Vim9 script: https://github.com/lacygoill/wiki/blob/master/vim/vim9.md |
|
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|
950 |
|
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|
951 If the script the function is defined in is Vim9 script, then script-local |
|
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|
952 variables can be accessed without the "s:" prefix. They must be defined |
| 20856 | 953 before the function is compiled. If the script the function is defined in is |
| 954 legacy script, then script-local variables must be accessed with the "s:" | |
| 24387 | 955 prefix if they do not exist at the time of compiling. |
|
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|
956 |
| 20552 | 957 *:defc* *:defcompile* |
| 958 :defc[ompile] Compile functions defined in the current script that | |
| 959 were not compiled yet. | |
| 960 This will report errors found during the compilation. | |
|
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|
961 |
| 19404 | 962 *:disa* *:disassemble* |
| 963 :disa[ssemble] {func} Show the instructions generated for {func}. | |
| 964 This is for debugging and testing. | |
|
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|
965 Note that for command line completion of {func} you |
|
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|
966 can prepend "s:" to find script-local functions. |
| 19404 | 967 |
| 23737 | 968 :disa[ssemble]! {func} Like `:disassemble` but with the instructions used for |
| 969 profiling. | |
| 970 | |
| 21250 | 971 Limitations ~ |
| 972 | |
| 973 Local variables will not be visible to string evaluation. For example: > | |
|
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974 def MapList(): list<string> |
|
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975 var list = ['aa', 'bb', 'cc', 'dd'] |
| 21250 | 976 return range(1, 2)->map('list[v:val]') |
| 977 enddef | |
| 978 | |
| 979 The map argument is a string expression, which is evaluated without the | |
| 980 function scope. Instead, use a lambda: > | |
|
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|
981 def MapList(): list<string> |
|
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982 var list = ['aa', 'bb', 'cc', 'dd'] |
|
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|
983 return range(1, 2)->map(( _, v) => list[v]) |
| 21250 | 984 enddef |
| 985 | |
|
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|
986 The same is true for commands that are not compiled, such as `:global`. |
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987 For these the backtick expansion can be used. Example: > |
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988 def Replace() |
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989 var newText = 'blah' |
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990 g/pattern/s/^/`=newText`/ |
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|
991 enddef |
| 21250 | 992 |
| 24278 | 993 Closures defined in a loop will share the same context. For example: > |
| 994 var flist: list<func> | |
| 995 for i in range(10) | |
| 996 var inloop = i | |
| 997 flist[i] = () => inloop | |
| 998 endfor | |
| 999 | |
| 1000 The "inloop" variable will exist only once, all closures put in the list refer | |
| 1001 to the same instance, which in the end will have the value 9. This is | |
| 1002 efficient. If you do want a separate context for each closure call a function | |
| 1003 to define it: > | |
| 1004 def GetFunc(i: number): func | |
| 1005 var inloop = i | |
| 1006 return () => inloop | |
| 1007 enddef | |
| 1008 | |
| 1009 var flist: list<func> | |
| 1010 for i in range(10) | |
| 1011 flist[i] = GetFunc(i) | |
| 1012 endfor | |
| 1013 | |
|
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1014 ============================================================================== |
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1015 |
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|
1016 4. Types *vim9-types* |
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1017 |
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1018 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1019 |
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|
1020 The following builtin types are supported: |
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1021 bool |
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1022 number |
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1023 float |
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|
1024 string |
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1025 blob |
|
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1026 list<{type}> |
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1027 dict<{type}> |
|
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1028 job |
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1029 channel |
| 19646 | 1030 func |
| 19968 | 1031 func: {type} |
|
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1032 func({type}, ...) |
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1033 func({type}, ...): {type} |
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1034 |
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1035 Not supported yet: |
|
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1036 tuple<a: {type}, b: {type}, ...> |
|
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1037 |
|
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1038 These types can be used in declarations, but no value will have this type: |
| 21499 | 1039 {type}|{type} {not implemented yet} |
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1040 void |
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1041 any |
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1042 |
|
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1043 There is no array type, use list<{type}> instead. For a list constant an |
|
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1044 efficient implementation is used that avoids allocating lot of small pieces of |
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1045 memory. |
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1046 |
|
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1047 A partial and function can be declared in more or less specific ways: |
|
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1048 func any kind of function reference, no type |
| 19968 | 1049 checking for arguments or return value |
|
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1050 func: {type} any number and type of arguments with specific |
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1051 return type |
| 19968 | 1052 func({type}) function with argument type, does not return |
|
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1053 a value |
| 19968 | 1054 func({type}): {type} function with argument type and return type |
| 1055 func(?{type}) function with type of optional argument, does | |
| 1056 not return a value | |
| 1057 func(...{type}) function with type of variable number of | |
| 1058 arguments, does not return a value | |
| 1059 func({type}, ?{type}, ...{type}): {type} | |
| 1060 function with: | |
| 1061 - type of mandatory argument | |
| 1062 - type of optional argument | |
| 1063 - type of variable number of arguments | |
| 1064 - return type | |
|
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1065 |
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1066 If the return type is "void" the function does not return a value. |
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1067 |
|
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1068 The reference can also be a |Partial|, in which case it stores extra arguments |
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1069 and/or a dictionary, which are not visible to the caller. Since they are |
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1070 called in the same way the declaration is the same. |
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1071 |
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1072 Custom types can be defined with `:type`: > |
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1073 :type MyList list<string> |
|
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1074 Custom types must start with a capital letter, to avoid name clashes with |
|
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1075 builtin types added later, similarly to user functions. |
|
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1076 {not implemented yet} |
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1077 |
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1078 And classes and interfaces can be used as types: > |
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1079 :class MyClass |
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1080 :var mine: MyClass |
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1081 |
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1082 :interface MyInterface |
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1083 :var mine: MyInterface |
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1084 |
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1085 :class MyTemplate<Targ> |
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1086 :var mine: MyTemplate<number> |
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1087 :var mine: MyTemplate<string> |
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1088 |
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1089 :class MyInterface<Targ> |
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1090 :var mine: MyInterface<number> |
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1091 :var mine: MyInterface<string> |
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1092 {not implemented yet} |
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1093 |
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1094 |
|
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1095 Variable types and type casting ~ |
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1096 *variable-types* |
|
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1097 Variables declared in Vim9 script or in a `:def` function have a type, either |
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1098 specified explicitly or inferred from the initialization. |
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1099 |
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1100 Global, buffer, window and tab page variables do not have a specific type, the |
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1101 value can be changed at any time, possibly changing the type. Therefore, in |
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1102 compiled code the "any" type is assumed. |
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1103 |
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1104 This can be a problem when the "any" type is undesired and the actual type is |
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1105 expected to always be the same. For example, when declaring a list: > |
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1106 var l: list<number> = [1, g:two] |
| 23305 | 1107 At compile time Vim doesn't know the type of "g:two" and the expression type |
| 1108 becomes list<any>. An instruction is generated to check the list type before | |
| 1109 doing the assignment, which is a bit inefficient. | |
| 1110 *type-casting* | |
| 1111 To avoid this, use a type cast: > | |
|
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1112 var l: list<number> = [1, <number>g:two] |
| 23305 | 1113 The compiled code will then only check that "g:two" is a number and give an |
| 1114 error if it isn't. This is called type casting. | |
|
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1115 |
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1116 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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1117 after the "<" or before the ">" (to avoid them being confused with |
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1118 smaller-than and bigger-than operators). |
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1119 |
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1120 The semantics is that, if needed, a runtime type check is performed. The |
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1121 value is not actually changed. If you need to change the type, e.g. to change |
|
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1122 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
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1123 string to a number. |
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1124 |
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1125 |
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1126 Type inference ~ |
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1127 *type-inference* |
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1128 In general: Whenever the type is clear it can be omitted. For example, when |
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1129 declaring a variable and giving it a value: > |
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1130 var name = 0 # infers number type |
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1131 var name = 'hello' # infers string type |
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1132 |
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1133 The type of a list and dictionary comes from the common type of the values. |
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1134 If the values all have the same type, that type is used for the list or |
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1135 dictionary. If there is a mix of types, the "any" type is used. > |
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1136 [1, 2, 3] list<number> |
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1137 ['a', 'b', 'c'] list<string> |
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1138 [1, 'x', 3] list<any> |
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1139 |
| 24387 | 1140 For script-local variables in Vim9 script the type is checked, also when the |
| 1141 variable was declared in a legacy function. | |
| 1142 | |
| 21991 | 1143 |
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1144 Stricter type checking ~ |
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1145 *type-checking* |
| 21991 | 1146 In legacy Vim script, where a number was expected, a string would be |
| 1147 automatically converted to a number. This was convenient for an actual number | |
| 24387 | 1148 such as "123", but leads to unexpected problems (and no error message) if the |
| 21991 | 1149 string doesn't start with a number. Quite often this leads to hard-to-find |
| 1150 bugs. | |
| 1151 | |
| 1152 In Vim9 script this has been made stricter. In most places it works just as | |
| 22171 | 1153 before, if the value used matches the expected type. There will sometimes be |
| 1154 an error, thus breaking backwards compatibility. For example: | |
| 21991 | 1155 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
| 1156 - Using a string value when setting a number options. | |
| 1157 - Using a number where a string is expected. *E1024* | |
| 1158 | |
| 23573 | 1159 One consequence is that the item type of a list or dict given to map() must |
| 24024 | 1160 not change. This will give an error in Vim9 script: > |
| 23573 | 1161 map([1, 2, 3], (i, v) => 'item ' .. i) |
| 24024 | 1162 E1012: Type mismatch; expected number but got string |
| 1163 Instead use |mapnew()|. If the item type was determined to be "any" it can | |
| 1164 change to a more specific type. E.g. when a list of mixed types gets changed | |
| 1165 to a list of numbers. | |
| 1166 Same for |extend()|, use |extendnew()| instead, and for |flatten()|, use | |
| 1167 |flattennew()| instead. | |
| 23573 | 1168 |
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1169 ============================================================================== |
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1170 |
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1171 5. Namespace, Import and Export |
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1172 *vim9script* *vim9-export* *vim9-import* |
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1173 |
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1174 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1175 |
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1176 A Vim9 script can be written to be imported. This means that everything in |
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1177 the script is local, unless exported. Those exported items, and only those |
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1178 items, can then be imported in another script. |
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1179 |
| 21991 | 1180 You can cheat by using the global namespace explicitly. We will assume here |
| 1181 that you don't do that. | |
| 1182 | |
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1183 |
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1184 Namespace ~ |
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1185 *vim9-namespace* |
| 19303 | 1186 To recognize a file that can be imported the `vim9script` statement must |
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1187 appear as the first statement in the file (see |vim9-mix| for an exception). |
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1188 It tells Vim to interpret the script in its own namespace, instead of the |
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1189 global namespace. If a file starts with: > |
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1190 vim9script |
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1191 var myvar = 'yes' |
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1192 Then "myvar" will only exist in this file. While without `vim9script` it would |
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1193 be available as `g:myvar` from any other script and function. |
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1194 |
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1195 The variables at the file level are very much like the script-local "s:" |
| 20115 | 1196 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
| 1197 deleted. | |
|
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1198 |
| 20115 | 1199 In Vim9 script the global "g:" namespace can still be used as before. And the |
| 1200 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
| 1201 declared and they can be deleted. | |
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1202 |
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1203 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
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1204 Vim default value, like with: > |
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1205 :set cpo&vim |
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1206 One of the effects is that |line-continuation| is always enabled. |
|
24150
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1207 The original value of 'cpoptions' is restored at the end of the script, while |
|
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1208 flags added or removed in the script are also added to or removed from the |
|
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1209 original value to get the same effect. The order of flags may change. |
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1210 |
|
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1211 *vim9-mix* |
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1212 There is one way to use both legacy and Vim9 syntax in one script file: > |
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1213 " comments may go here |
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1214 if !has('vim9script') |
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1215 " legacy script commands go here |
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1216 finish |
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1217 endif |
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1218 vim9script |
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1219 # Vim9 script commands go here |
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1220 This allows for writing a script that takes advantage of the Vim9 script |
| 24024 | 1221 syntax if possible, but will also work on a Vim version without it. |
|
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1222 |
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1223 This can only work in two ways: |
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1224 1. The "if" statement evaluates to false, the commands up to `endif` are |
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1225 skipped and `vim9script` is then the first command actually executed. |
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1226 2. The "if" statement evaluates to true, the commands up to `endif` are |
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1227 executed and `finish` bails out before reaching `vim9script`. |
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1228 |
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1229 TODO: The "vim9script" feature does not exist yet, it will only be added once |
|
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1230 the Vim9 script syntax has been fully implemented. |
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1231 |
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1232 |
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1233 Export ~ |
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1234 *:export* *:exp* |
| 21499 | 1235 Exporting an item can be written as: > |
|
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1236 export const EXPORTED_CONST = 1234 |
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1237 export var someValue = ... |
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1238 export final someValue = ... |
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1239 export const someValue = ... |
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1240 export def MyFunc() ... |
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1241 export class MyClass ... |
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1242 |
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1243 As this suggests, only constants, variables, `:def` functions and classes can |
| 24103 | 1244 be exported. {not implemented yet: export class} |
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1245 |
| 20856 | 1246 *E1042* |
| 1247 `:export` can only be used in Vim9 script, at the script level. | |
|
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1248 |
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1249 |
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1250 Import ~ |
| 20965 | 1251 *:import* *:imp* *E1094* |
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1252 The exported items can be imported individually in another Vim9 script: > |
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1253 import EXPORTED_CONST from "thatscript.vim" |
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1254 import MyClass from "myclass.vim" |
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1255 |
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1256 To import multiple items at the same time: > |
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1257 import {someValue, MyClass} from "thatscript.vim" |
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1258 |
| 19303 | 1259 In case the name is ambiguous, another name can be specified: > |
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1260 import MyClass as ThatClass from "myclass.vim" |
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1261 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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1262 |
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1263 To import all exported items under a specific identifier: > |
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1264 import * as That from 'thatscript.vim' |
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1265 |
| 22328 | 1266 {not implemented yet: using "This as That"} |
| 1267 | |
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1268 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
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1269 to choose the name "That", but it is highly recommended to use the name of the |
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1270 script file to avoid confusion. |
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1271 |
| 22171 | 1272 `:import` can also be used in legacy Vim script. The imported items still |
| 1273 become script-local, even when the "s:" prefix is not given. | |
| 1274 | |
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1275 The script name after `import` can be: |
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1276 - A relative path, starting "." or "..". This finds a file relative to the |
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1277 location of the script file itself. This is useful to split up a large |
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1278 plugin into several files. |
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1279 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
| 22723 | 1280 will rarely be used. |
|
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1281 - A path not being relative or absolute. This will be found in the |
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1282 "import" subdirectories of 'runtimepath' entries. The name will usually be |
|
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1283 longer and unique, to avoid loading the wrong file. |
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1284 |
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1285 Once a vim9 script file has been imported, the result is cached and used the |
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1286 next time the same script is imported. It will not be read again. |
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1287 *:import-cycle* |
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1288 The `import` commands are executed when encountered. If that script (directly |
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1289 or indirectly) imports the current script, then items defined after the |
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1290 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
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1291 result in undefined items. |
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1292 |
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1293 |
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1294 Import in an autoload script ~ |
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1295 |
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1296 For optimal startup speed, loading scripts should be postponed until they are |
| 19303 | 1297 actually needed. A recommended mechanism: |
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1298 |
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1299 1. In the plugin define user commands, functions and/or mappings that refer to |
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1300 an autoload script. > |
| 23666 | 1301 command -nargs=1 SearchForStuff searchfor#Stuff(<f-args>) |
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1302 |
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1303 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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1304 |
| 21825 | 1305 2. In the autoload script do the actual work. You can import items from |
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1306 other files to split up functionality in appropriate pieces. > |
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1307 vim9script |
| 23573 | 1308 import FilterFunc from "../import/someother.vim" |
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1309 def searchfor#Stuff(arg: string) |
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1310 var filtered = FilterFunc(arg) |
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1311 ... |
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1312 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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1313 must be exactly the same as the prefix for the function name, that is how |
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1314 Vim finds the file. |
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1315 |
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1316 3. Other functionality, possibly shared between plugins, contains the exported |
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1317 items and any private items. > |
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1318 vim9script |
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1319 var localVar = 'local' |
| 22171 | 1320 export def FilterFunc(arg: string): string |
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1321 ... |
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1322 < This goes in .../import/someother.vim. |
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1323 |
|
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1324 When compiling a `:def` function and a function in an autoload script is |
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1325 encountered, the script is not loaded until the `:def` function is called. |
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1326 |
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1327 |
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1328 Import in legacy Vim script ~ |
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1329 |
| 20856 | 1330 If an `import` statement is used in legacy Vim script, the script-local "s:" |
| 1331 namespace will be used for the imported item, even when "s:" is not specified. | |
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1332 |
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1333 |
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1334 ============================================================================== |
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1335 |
| 22328 | 1336 6. Future work: classes *vim9-classes* |
| 1337 | |
| 1338 Above "class" was mentioned a few times, but it has not been implemented yet. | |
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1339 Most of Vim9 script can be created without this functionality, and since |
| 22328 | 1340 implementing classes is going to be a lot of work, it is left for the future. |
| 1341 For now we'll just make sure classes can be added later. | |
| 1342 | |
| 1343 Thoughts: | |
| 1344 - `class` / `endclass`, everything in one file | |
| 1345 - Class names are always CamelCase | |
| 1346 - Single constructor | |
| 1347 - Single inheritance with `class ThisClass extends BaseClass` | |
| 1348 - `abstract class` | |
| 1349 - `interface` (Abstract class without any implementation) | |
| 1350 - `class SomeClass implements SomeInterface` | |
| 1351 - Generics for class: `class <Tkey, Tentry>` | |
| 1352 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
| 1353 | |
| 1354 Again, much of this is from TypeScript. | |
| 1355 | |
| 1356 Some things that look like good additions: | |
| 1357 - Use a class as an interface (like Dart) | |
| 1358 - Extend a class with methods, using an import (like Dart) | |
| 1359 | |
| 1360 An important class that will be provided is "Promise". Since Vim is single | |
| 1361 threaded, connecting asynchronous operations is a natural way of allowing | |
| 1362 plugins to do their work without blocking the user. It's a uniform way to | |
| 1363 invoke callbacks and handle timeouts and errors. | |
| 1364 | |
| 1365 ============================================================================== | |
| 1366 | |
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1367 9. Rationale *vim9-rationale* |
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1368 |
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1369 The :def command ~ |
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1370 |
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1371 Plugin writers have asked for much faster Vim script. Investigations have |
| 19303 | 1372 shown that keeping the existing semantics of function calls make this close to |
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1373 impossible, because of the overhead involved with calling a function, setting |
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1374 up the local function scope and executing lines. There are many details that |
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1375 need to be handled, such as error messages and exceptions. The need to create |
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1376 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1377 much overhead that cannot be avoided. |
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1378 |
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1379 Therefore the `:def` method to define a new-style function had to be added, |
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1380 which allows for a function with different semantics. Most things still work |
|
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1381 as before, but some parts do not. A new way to define a function was |
|
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1382 considered the best way to separate the legacy style code from Vim9 style code. |
|
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1383 |
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1384 Using "def" to define a function comes from Python. Other languages use |
|
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1385 "function" which clashes with legacy Vim script. |
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1386 |
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1387 |
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1388 Type checking ~ |
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1389 |
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|
1390 When compiling lines of Vim commands into instructions as much as possible |
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1391 should be done at compile time. Postponing it to runtime makes the execution |
|
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1392 slower and means mistakes are found only later. For example, when |
|
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1393 encountering the "+" character and compiling this into a generic add |
| 23666 | 1394 instruction, at runtime the instruction would have to inspect the type of the |
| 1395 arguments and decide what kind of addition to do. And when the type is | |
| 1396 dictionary throw an error. If the types are known to be numbers then an "add | |
| 1397 number" instruction can be used, which is faster. The error can be given at | |
| 1398 compile time, no error handling is needed at runtime, since adding two numbers | |
| 1399 cannot fail. | |
|
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1400 |
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1401 The syntax for types, using <type> for compound types, is similar to Java. It |
|
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1402 is easy to understand and widely used. The type names are what were used in |
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|
1403 Vim before, with some additions such as "void" and "bool". |
|
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1404 |
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1405 |
| 22328 | 1406 Removing clutter and weirdness ~ |
| 20856 | 1407 |
| 22328 | 1408 Once decided that `:def` functions have different syntax than legacy functions, |
| 1409 we are free to add improvements to make the code more familiar for users who | |
| 1410 know popular programming languages. In other words: remove weird things that | |
|
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1411 only Vim does. |
| 22328 | 1412 |
| 1413 We can also remove clutter, mainly things that were done to make Vim script | |
|
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|
1414 backwards compatible with the good old Vi commands. |
| 20856 | 1415 |
| 22328 | 1416 Examples: |
| 1417 - Drop `:call` for calling a function and `:eval` for manipulating data. | |
| 1418 - Drop using a leading backslash for line continuation, automatically figure | |
| 1419 out where an expression ends. | |
| 20856 | 1420 |
| 22328 | 1421 However, this does require that some things need to change: |
| 1422 - Comments start with # instead of ", to avoid confusing them with strings. | |
|
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1423 This is good anyway, it is known from several popular languages. |
| 22328 | 1424 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
| 1425 expressions (single quote can be a string or a mark, "/" can be divide or a | |
| 1426 search command, etc.). | |
| 1427 | |
| 1428 Goal is to limit the differences. A good criteria is that when the old syntax | |
|
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1429 is accidentally used you are very likely to get an error message. |
| 20856 | 1430 |
| 1431 | |
|
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1432 Syntax and semantics from popular languages ~ |
|
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1433 |
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1434 Script writers have complained that the Vim script syntax is unexpectedly |
|
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1435 different from what they are used to. To reduce this complaint popular |
| 20856 | 1436 languages are used as an example. At the same time, we do not want to abandon |
| 1437 the well-known parts of legacy Vim script. | |
|
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1438 |
|
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1439 For many things TypeScript is followed. It's a recent language that is |
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1440 gaining popularity and has similarities with Vim script. It also has a |
| 22328 | 1441 mix of static typing (a variable always has a known value type) and dynamic |
|
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1442 typing (a variable can have different types, this changes at runtime). Since |
| 22328 | 1443 legacy Vim script is dynamically typed and a lot of existing functionality |
| 1444 (esp. builtin functions) depends on that, while static typing allows for much | |
| 1445 faster execution, we need to have this mix in Vim9 script. | |
| 1446 | |
| 22171 | 1447 There is no intention to completely match TypeScript syntax and semantics. We |
| 1448 just want to take those parts that we can use for Vim and we expect Vim users | |
| 22328 | 1449 will be happy with. TypeScript is a complex language with its own history, |
| 1450 advantages and disadvantages. To get an idea of the disadvantages read the | |
| 1451 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
|
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1452 parts" and read the "Things to avoid" section. |
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1453 |
| 22328 | 1454 People familiar with other languages (Java, Python, etc.) will also find |
| 1455 things in TypeScript that they do not like or do not understand. We'll try to | |
| 1456 avoid those things. | |
|
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1457 |
|
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|
1458 Specific items from TypeScript we avoid: |
|
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1459 - Overloading "+", using it both for addition and string concatenation. This |
|
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|
1460 goes against legacy Vim script and often leads to mistakes. For that reason |
|
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1461 we will keep using ".." for string concatenation. Lua also uses ".." this |
|
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1462 way. And it allows for conversion to string for more values. |
|
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1463 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
|
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|
1464 cannot assign the value to a boolean. That is inconsistent and can be |
|
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1465 annoying. Vim recognizes an expression with && or || and allows using the |
|
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|
1466 result as a bool. TODO: to be reconsidered |
|
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1467 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
|
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|
1468 Truthy. That is inconsistent. In Vim an empty list and dict are also |
|
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1469 Falsy. |
|
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1470 - TypeScript has various "Readonly" types, which have limited usefulness, |
|
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1471 since a type cast can remove the immutable nature. Vim locks the value, |
|
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1472 which is more flexible, but is only checked at runtime. |
| 22171 | 1473 |
|
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1474 |
|
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1475 Declarations ~ |
|
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1476 |
|
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1477 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
|
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1478 are used. That is different, thus it's good to use a different command: |
|
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|
1479 `:var`. This is used in many languages. The semantics might be slightly |
|
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1480 different, but it's easily recognized as a declaration. |
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1481 |
| 23047 | 1482 Using `:const` for constants is common, but the semantics varies. Some |
|
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1483 languages only make the variable immutable, others also make the value |
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1484 immutable. Since "final" is well known from Java for only making the variable |
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1485 immutable we decided to use that. And then `:const` can be used for making |
|
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1486 both immutable. This was also used in legacy Vim script and the meaning is |
|
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1487 almost the same. |
|
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1488 |
|
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1489 What we end up with is very similar to Dart: > |
|
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1490 :var name # mutable variable and value |
|
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1491 :final name # immutable variable, mutable value |
|
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1492 :const name # immutable variable and value |
|
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1493 |
|
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1494 Since legacy and Vim9 script will be mixed and global variables will be |
|
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1495 shared, optional type checking is desirable. Also, type inference will avoid |
|
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1496 the need for specifying the type in many cases. The TypeScript syntax fits |
|
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1497 best for adding types to declarations: > |
|
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1498 var name: string # string type is specified |
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1499 ... |
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1500 name = 'John' |
|
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1501 const greeting = 'hello' # string type is inferred |
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1502 |
|
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1503 This is how we put types in a declaration: > |
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1504 var mylist: list<string> |
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1505 final mylist: list<string> = ['foo'] |
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1506 def Func(arg1: number, arg2: string): bool |
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1507 |
|
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1508 Two alternatives were considered: |
|
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1509 1. Put the type before the name, like Dart: > |
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1510 var list<string> mylist |
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1511 final list<string> mylist = ['foo'] |
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1512 def Func(number arg1, string arg2) bool |
|
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1513 2. Put the type after the variable name, but do not use a colon, like Go: > |
|
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1514 var mylist list<string> |
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1515 final mylist list<string> = ['foo'] |
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1516 def Func(arg1 number, arg2 string) bool |
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1517 |
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1518 The first is more familiar for anyone used to C or Java. The second one |
| 22565 | 1519 doesn't really have an advantage over the first, so let's discard the second. |
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1520 |
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1521 Since we use type inference the type can be left out when it can be inferred |
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1522 from the value. This means that after `var` we don't know if a type or a name |
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1523 follows. That makes parsing harder, not only for Vim but also for humans. |
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1524 Also, it will not be allowed to use a variable name that could be a type name, |
|
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1525 using `var string string` is too confusing. |
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1526 |
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1527 The chosen syntax, using a colon to separate the name from the type, adds |
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1528 punctuation, but it actually makes it easier to recognize the parts of a |
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1529 declaration. |
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1530 |
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1531 |
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1532 Expressions ~ |
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1533 |
| 22565 | 1534 Expression evaluation was already close to what other languages are doing. |
| 1535 Some details are unexpected and can be improved. For example a boolean | |
| 1536 condition would accept a string, convert it to a number and check if the | |
| 1537 number is non-zero. This is unexpected and often leads to mistakes, since | |
| 1538 text not starting with a number would be converted to zero, which is | |
| 22723 | 1539 considered false. Thus using a string for a condition would often not give an |
| 1540 error and be considered false. That is confusing. | |
|
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1541 |
| 23047 | 1542 In Vim9 type checking is stricter to avoid mistakes. Where a condition is |
| 22565 | 1543 used, e.g. with the `:if` command and the `||` operator, only boolean-like |
| 1544 values are accepted: | |
| 1545 true: `true`, `v:true`, `1`, `0 < 9` | |
| 1546 false: `false`, `v:false`, `0`, `0 > 9` | |
| 1547 Note that the number zero is false and the number one is true. This is more | |
| 22723 | 1548 permissive than most other languages. It was done because many builtin |
| 22565 | 1549 functions return these values. |
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1550 |
| 22565 | 1551 If you have any type of value and want to use it as a boolean, use the `!!` |
| 1552 operator: | |
| 1553 true: !`!'text'`, `!![99]`, `!!{'x': 1}`, `!!99` | |
| 1554 false: `!!''`, `!![]`, `!!{}` | |
| 1555 | |
| 1556 From a language like JavaScript we have this handy construct: > | |
| 1557 GetName() || 'unknown' | |
| 1558 However, this conflicts with only allowing a boolean for a condition. | |
| 1559 Therefore the "??" operator was added: > | |
| 1560 GetName() ?? 'unknown' | |
| 1561 Here you can explicitly express your intention to use the value as-is and not | |
| 1562 result in a boolean. This is called the |falsy-operator|. | |
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1563 |
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1564 |
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1565 Import and Export ~ |
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1566 |
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1567 A problem of legacy Vim script is that by default all functions and variables |
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1568 are global. It is possible to make them script-local, but then they are not |
| 22171 | 1569 available in other scripts. This defies the concept of a package that only |
| 1570 exports selected items and keeps the rest local. | |
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1571 |
| 21825 | 1572 In Vim9 script a mechanism very similar to the JavaScript import and export |
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1573 mechanism is supported. It is a variant to the existing `:source` command |
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1574 that works like one would expect: |
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1575 - Instead of making everything global by default, everything is script-local, |
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1576 unless exported. |
| 22171 | 1577 - When importing a script the symbols that are imported are explicitly listed, |
| 1578 avoiding name conflicts and failures if functionality is added later. | |
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1579 - The mechanism allows for writing a big, long script with a very clear API: |
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1580 the exported function(s) and class(es). |
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1581 - By using relative paths loading can be much faster for an import inside of a |
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1582 package, no need to search many directories. |
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1583 - Once an import has been used, it can be cached and loading it again can be |
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1584 avoided. |
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1585 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1586 |
| 20856 | 1587 When sourcing a Vim9 script from a legacy script, only the items defined |
| 1588 globally can be used, not the exported items. Alternatives considered: | |
| 1589 - All the exported items become available as script-local items. This makes | |
| 22171 | 1590 it uncontrollable what items get defined and likely soon leads to trouble. |
| 20856 | 1591 - Use the exported items and make them global. Disadvantage is that it's then |
| 1592 not possible to avoid name clashes in the global namespace. | |
| 1593 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
| 1594 makes it difficult to use scripts for testing, or sourcing them from the | |
| 1595 command line to try them out. | |
| 22171 | 1596 Note that you can also use `:import` in legacy Vim script, see above. |
| 20856 | 1597 |
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1598 |
| 22328 | 1599 Compiling functions early ~ |
| 1600 | |
| 1601 Functions are compiled when called or when `:defcompile` is used. Why not | |
| 1602 compile them early, so that syntax and type errors are reported early? | |
| 1603 | |
| 1604 The functions can't be compiled right away when encountered, because there may | |
| 1605 be forward references to functions defined later. Consider defining functions | |
| 1606 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
| 1607 to reorder the functions to avoid forward references. | |
| 1608 | |
| 1609 An alternative would be to first scan through the file to locate items and | |
| 1610 figure out their type, so that forward references are found, and only then | |
| 1611 execute the script and compile the functions. This means the script has to be | |
| 1612 parsed twice, which is slower, and some conditions at the script level, such | |
| 1613 as checking if a feature is supported, are hard to use. An attempt was made | |
| 1614 to see if it works, but it turned out to be impossible to make work nicely. | |
| 1615 | |
| 1616 It would be possible to compile all the functions at the end of the script. | |
| 1617 The drawback is that if a function never gets called, the overhead of | |
| 1618 compiling it counts anyway. Since startup speed is very important, in most | |
| 1619 cases it's better to do it later and accept that syntax and type errors are | |
| 1620 only reported then. In case these errors should be found early, e.g. when | |
| 1621 testing, the `:defcompile` command will help out. | |
| 1622 | |
| 1623 | |
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1624 Why not use an embedded language? ~ |
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1625 |
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1626 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
| 22328 | 1627 these interfaces have never become widely used, for various reasons. When |
| 1628 Vim9 was designed a decision was made to make these interfaces lower priority | |
| 1629 and concentrate on Vim script. | |
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1630 |
| 22328 | 1631 Still, plugin writers may find other languages more familiar, want to use |
| 1632 existing libraries or see a performance benefit. We encourage plugin authors | |
| 1633 to write code in any language and run it as an external tool, using jobs and | |
| 1634 channels. We can try to make this easier somehow. | |
| 1635 | |
| 1636 Using an external tool also has disadvantages. An alternative is to convert | |
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1637 the tool into Vim script. For that to be possible without too much |
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1638 translation, and keeping the code fast at the same time, the constructs of the |
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1639 tool need to be supported. Since most languages support classes the lack of |
| 22171 | 1640 support for classes in Vim is then a problem. |
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1641 |
| 22328 | 1642 |
| 1643 Classes ~ | |
| 1644 | |
| 1645 Vim supports a kind-of object oriented programming by adding methods to a | |
| 1646 dictionary. With some care this can be made to work, but it does not look | |
| 1647 like real classes. On top of that, it's quite slow, because of the use of | |
| 1648 dictionaries. | |
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1649 |
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1650 The support of classes in Vim9 script is a "minimal common functionality" of |
| 22171 | 1651 class support in most languages. It works much like Java, which is the most |
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1652 popular programming language. |
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1653 |
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1654 |
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1655 |
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1656 vim:tw=78:ts=8:noet:ft=help:norl: |