Mercurial > vim
annotate runtime/doc/vim9.txt @ 24024:ef454a7f485d
Update runtime files.
Commit: https://github.com/vim/vim/commit/9faec4e3d439968e21ad74e917aebb289df8f849
Author: Bram Moolenaar <Bram@vim.org>
Date: Sat Feb 27 16:38:07 2021 +0100
Update runtime files.
author | Bram Moolenaar <Bram@vim.org> |
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date | Sat, 27 Feb 2021 16:45:04 +0100 |
parents | 54b2aa1f0d42 |
children | 788e10cec9bd |
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24024 | 1 *vim9.txt* For Vim version 8.2. Last change: 2021 Feb 23 |
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4 VIM REFERENCE MANUAL by Bram Moolenaar |
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7 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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8 |
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9 Vim9 script commands and expressions. *Vim9* *vim9* |
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10 |
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11 Most expression help is in |eval.txt|. This file is about the new syntax and |
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12 features in Vim9 script. |
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13 |
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14 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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23466 | 17 1. What is Vim9 script? |Vim9-script| |
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18 2. Differences |vim9-differences| |
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19 3. New style functions |fast-functions| |
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20 4. Types |vim9-types| |
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21 5. Namespace, Import and Export |vim9script| |
22328 | 22 6. Future work: classes |vim9-classes| |
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23 |
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24 9. Rationale |vim9-rationale| |
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25 |
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26 ============================================================================== |
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27 |
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28 1. What is Vim9 script? *Vim9-script* |
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29 |
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30 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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31 |
20241 | 32 Vim script has been growing over time, while preserving backwards |
33 compatibility. That means bad choices from the past often can't be changed | |
20965 | 34 and compatibility with Vi restricts possible solutions. Execution is quite |
20241 | 35 slow, each line is parsed every time it is executed. |
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36 |
20241 | 37 The main goal of Vim9 script is to drastically improve performance. This is |
38 accomplished by compiling commands into instructions that can be efficiently | |
39 executed. An increase in execution speed of 10 to 100 times can be expected. | |
40 | |
41 A secondary goal is to avoid Vim-specific constructs and get closer to | |
42 commonly used programming languages, such as JavaScript, TypeScript and Java. | |
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43 |
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44 The performance improvements can only be achieved by not being 100% backwards |
20552 | 45 compatible. For example, making function arguments available in the |
46 "a:" dictionary adds quite a lot of overhead. In a Vim9 function this | |
47 dictionary is not available. Other differences are more subtle, such as how | |
48 errors are handled. | |
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49 |
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50 The Vim9 script syntax and semantics are used in: |
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51 - a function defined with the `:def` command |
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52 - a script file where the first command is `vim9script` |
22328 | 53 - an autocommand defined in the context of the above |
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54 - a command prefixed with the `vim9cmd` command modifier |
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23573 | 56 When using `:function` in a Vim9 script file the legacy syntax is used, with |
57 the highest |scriptversion|. However, this can be confusing and is therefore | |
58 discouraged. | |
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59 |
20241 | 60 Vim9 script and legacy Vim script can be mixed. There is no requirement to |
22328 | 61 rewrite old scripts, they keep working as before. You may want to use a few |
62 `:def` functions for code that needs to be fast. | |
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63 |
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64 *:vim9* *:vim9cmd* |
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65 :vim9[cmd] {cmd} |
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66 Execute {cmd} using Vim9 script syntax and semantics. |
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67 Useful when typing a command and in a legacy script or |
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68 function. |
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69 |
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70 ============================================================================== |
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71 |
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72 2. Differences from legacy Vim script *vim9-differences* |
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73 |
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74 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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22441 | 76 Overview ~ |
77 | |
78 Brief summary of the differences you will most often encounter when using Vim9 | |
79 script and `:def` functions; details are below: | |
80 - Comments start with #, not ": > | |
23573 | 81 echo "hello" # comment |
22441 | 82 - Using a backslash for line continuation is hardly ever needed: > |
23573 | 83 echo "hello " |
22441 | 84 .. yourName |
85 .. ", how are you?" | |
86 - White space is required in many places. | |
87 - Assign values without `:let`, declare variables with `:var`: > | |
23573 | 88 var count = 0 |
22441 | 89 count += 3 |
90 - Constants can be declared with `:final` and `:const`: > | |
23573 | 91 final matches = [] # add matches |
22441 | 92 const names = ['Betty', 'Peter'] # cannot be changed |
93 - `:final` cannot be used as an abbreviation of `:finally`. | |
94 - Variables and functions are script-local by default. | |
95 - Functions are declared with argument types and return type: > | |
96 def CallMe(count: number, message: string): bool | |
97 - Call functions without `:call`: > | |
23573 | 98 writefile(['done'], 'file.txt') |
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99 - You cannot use `:xit`, `:t`, `:k`, `:append`, `:change`, `:insert` or |
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100 curly-braces names. |
22441 | 101 - A range before a command must be prefixed with a colon: > |
23573 | 102 :%s/this/that |
103 - Unless mentioned specifically, the highest |scriptversion| is used. | |
22441 | 104 |
105 | |
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106 Comments starting with # ~ |
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107 |
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108 In legacy Vim script comments start with double quote. In Vim9 script |
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109 comments start with #. > |
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110 # declarations |
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111 var count = 0 # number of occurrences |
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112 |
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113 The reason is that a double quote can also be the start of a string. In many |
21825 | 114 places, especially halfway through an expression with a line break, it's hard |
115 to tell what the meaning is, since both a string and a comment can be followed | |
116 by arbitrary text. To avoid confusion only # comments are recognized. This | |
117 is the same as in shell scripts and Python programs. | |
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118 |
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119 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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120 `:number` for that. > |
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121 101 number |
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122 |
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123 To improve readability there must be a space between a command and the # |
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124 that starts a comment: > |
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125 var name = value # comment |
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126 var name = value# error! |
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127 |
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128 In legacy Vim script # is also used for the alternate file name. In Vim9 |
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129 script you need to use %% instead. Instead of ## use %%% (stands for all |
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130 arguments). |
20115 | 131 |
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132 |
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133 Vim9 functions ~ |
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134 |
20241 | 135 A function defined with `:def` is compiled. Execution is many times faster, |
136 often 10x to 100x times. | |
137 | |
20552 | 138 Many errors are already found when compiling, before the function is executed. |
20241 | 139 The syntax is strict, to enforce code that is easy to read and understand. |
140 | |
23164 | 141 Compilation is done when either of these is encountered: |
142 - the first time the function is called | |
21991 | 143 - when the `:defcompile` command is encountered in the script where the |
144 function was defined | |
145 - `:disassemble` is used for the function. | |
146 - a function that is compiled calls the function or uses it as a function | |
147 reference | |
20552 | 148 |
149 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
23164 | 150 "closure". A `:def` function always aborts on an error (unless `:silent!` was |
151 used for the command or inside a `:try` block), does not get a range passed | |
23305 | 152 cannot be a "dict" function, and can always be a closure. |
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153 |
20241 | 154 The argument types and return type need to be specified. The "any" type can |
155 be used, type checking will then be done at runtime, like with legacy | |
156 functions. | |
157 | |
21825 | 158 Arguments are accessed by name, without "a:", just like any other language. |
159 There is no "a:" dictionary or "a:000" list. | |
20241 | 160 |
161 Variable arguments are defined as the last argument, with a name and have a | |
21825 | 162 list type, similar to TypeScript. For example, a list of numbers: > |
22171 | 163 def MyFunc(...itemlist: list<number>) |
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164 for item in itemlist |
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165 ... |
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166 |
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167 |
20241 | 168 Functions and variables are script-local by default ~ |
20856 | 169 *vim9-scopes* |
20115 | 170 When using `:function` or `:def` to specify a new function at the script level |
171 in a Vim9 script, the function is local to the script, as if "s:" was | |
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172 prefixed. Using the "s:" prefix is optional. To define a global function or |
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173 variable the "g:" prefix must be used. For functions in an autoload script |
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174 the "name#" prefix is sufficient. > |
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175 def ThisFunction() # script-local |
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176 def s:ThisFunction() # script-local |
22171 | 177 def g:ThatFunction() # global |
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178 def scriptname#function() # autoload |
20115 | 179 |
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180 When using `:function` or `:def` to specify a nested function inside a `:def` |
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181 function, this nested function is local to the code block it is defined in. |
22565 | 182 In a `:def` function it is not possible to define a script-local function. It |
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183 is possible to define a global function by using the "g:" prefix. |
20115 | 184 |
185 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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186 search for the function: |
22565 | 187 - in the function scope, in block scopes |
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188 - in the script scope, possibly imported |
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189 - in the list of global functions |
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190 However, it is recommended to always use "g:" to refer to a global function |
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191 for clarity. |
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192 |
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193 In all cases the function must be defined before used. That is when it is |
22723 | 194 called, when `:defcompile` causes it to be compiled, or when code that calls |
195 it is being compiled (to figure out the return type). | |
20241 | 196 |
21676 | 197 The result is that functions and variables without a namespace can usually be |
20241 | 198 found in the script, either defined there or imported. Global functions and |
21676 | 199 variables could be defined anywhere (good luck finding out where!). |
20115 | 200 |
21825 | 201 Global functions can still be defined and deleted at nearly any time. In |
20317 | 202 Vim9 script script-local functions are defined once when the script is sourced |
20552 | 203 and cannot be deleted or replaced. |
20115 | 204 |
23305 | 205 When compiling a function and a function call is encountered for a function |
206 that is not (yet) defined, the |FuncUndefined| autocommand is not triggered. | |
207 You can use an autoload function if needed, or call a legacy function and have | |
208 |FuncUndefined| triggered there. | |
209 | |
20115 | 210 |
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211 Reloading a Vim9 script clears functions and variables by default ~ |
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212 *vim9-reload* |
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213 When loading a legacy Vim script a second time nothing is removed, the |
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214 commands will replace existing variables and functions and create new ones. |
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215 |
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216 When loading a Vim9 script a second time all existing script-local functions |
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217 and variables are deleted, thus you start with a clean slate. This is useful |
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218 if you are developing a plugin and want to try a new version. If you renamed |
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219 something you don't have to worry about the old name still hanging around. |
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220 |
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221 If you do want to keep items, use: > |
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222 vim9script noclear |
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223 |
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224 You want to use this in scripts that use a `finish` command to bail out at |
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225 some point when loaded again. E.g. when a buffer local option is set: > |
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226 vim9script noclear |
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227 setlocal completefunc=SomeFunc |
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228 if exists('*g:SomeFunc') | finish | endif |
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229 def g:SomeFunc() |
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230 .... |
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231 |
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232 |
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233 Variable declarations with :var, :final and :const ~ |
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234 *vim9-declaration* *:var* |
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235 Local variables need to be declared with `:var`. Local constants need to be |
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236 declared with `:final` or `:const`. We refer to both as "variables" in this |
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237 section. |
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238 |
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239 Variables can be local to a script, function or code block: > |
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240 vim9script |
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241 var script_var = 123 |
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242 def SomeFunc() |
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243 var func_var = script_var |
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244 if cond |
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245 var block_var = func_var |
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246 ... |
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247 |
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248 The variables are only visible in the block where they are defined and nested |
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249 blocks. Once the block ends the variable is no longer accessible: > |
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250 if cond |
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251 var inner = 5 |
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252 else |
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253 var inner = 0 |
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254 endif |
22171 | 255 echo inner # Error! |
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256 |
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257 The declaration must be done earlier: > |
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258 var inner: number |
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259 if cond |
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260 inner = 5 |
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261 else |
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262 inner = 0 |
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263 endif |
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264 echo inner |
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265 |
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266 To intentionally hide a variable from code that follows, a block can be |
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267 used: > |
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268 { |
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269 var temp = 'temp' |
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270 ... |
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271 } |
22171 | 272 echo temp # Error! |
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273 |
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274 Declaring a variable with a type but without an initializer will initialize to |
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275 zero, false or empty. |
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276 |
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277 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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278 without any command. The same for global, window, tab, buffer and Vim |
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279 variables, because they are not really declared. They can also be deleted |
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280 with `:unlet`. |
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281 |
24024 | 282 Variables, functions and function arguments cannot shadow previously defined |
283 or imported variables and functions in the same script file. | |
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284 Variables may shadow Ex commands, rename the variable if needed. |
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285 |
20241 | 286 Global variables and user defined functions must be prefixed with "g:", also |
287 at the script level. > | |
19968 | 288 vim9script |
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289 var script_local = 'text' |
21499 | 290 g:global = 'value' |
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291 var Funcref = g:ThatFunction |
19968 | 292 |
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293 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
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294 used to repeat a `:substitute` command. |
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295 |
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296 |
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297 Constants ~ |
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298 *vim9-const* *vim9-final* |
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299 How constants work varies between languages. Some consider a variable that |
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300 can't be assigned another value a constant. JavaScript is an example. Others |
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301 also make the value immutable, thus when a constant uses a list, the list |
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302 cannot be changed. In Vim9 we can use both. |
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303 |
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304 `:const` is used for making both the variable and the value a constant. Use |
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305 this for composite structures that you want to make sure will not be modified. |
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306 Example: > |
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307 const myList = [1, 2] |
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308 myList = [3, 4] # Error! |
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309 myList[0] = 9 # Error! |
24024 | 310 myList->add(3) # Error! |
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311 < *:final* |
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312 `:final` is used for making only the variable a constant, the value can be |
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313 changed. This is well known from Java. Example: > |
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314 final myList = [1, 2] |
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315 myList = [3, 4] # Error! |
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316 myList[0] = 9 # OK |
24024 | 317 myList->add(3) # OK |
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318 |
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319 It is common to write constants as ALL_CAPS, but you don't have to. |
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320 |
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321 The constant only applies to the value itself, not what it refers to. > |
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322 final females = ["Mary"] |
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323 const NAMES = [["John", "Peter"], females] |
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324 NAMES[0] = ["Jack"] # Error! |
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325 NAMES[0][0] = "Jack" # Error! |
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326 NAMES[1] = ["Emma"] # Error! |
23573 | 327 NAMES[1][0] = "Emma" # OK, now females[0] == "Emma" |
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328 |
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329 < *E1092* |
21499 | 330 Declaring more than one variable at a time, using the unpack notation, is |
331 currently not supported: > | |
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332 var [v1, v2] = GetValues() # Error! |
21499 | 333 That is because the type needs to be inferred from the list item type, which |
334 isn't that easy. | |
335 | |
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336 |
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337 Omitting :call and :eval ~ |
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338 |
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339 Functions can be called without `:call`: > |
22171 | 340 writefile(lines, 'file') |
19303 | 341 Using `:call` is still possible, but this is discouraged. |
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342 |
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343 A method call without `eval` is possible, so long as the start is an |
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344 identifier or can't be an Ex command. Examples: > |
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345 myList->add(123) |
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346 g:myList->add(123) |
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347 [1, 2, 3]->Process() |
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348 {a: 1, b: 2}->Process() |
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349 "foobar"->Process() |
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350 ("foobar")->Process() |
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351 'foobar'->Process() |
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352 ('foobar')->Process() |
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353 |
21825 | 354 In the rare case there is ambiguity between a function name and an Ex command, |
21676 | 355 prepend ":" to make clear you want to use the Ex command. For example, there |
356 is both the `:substitute` command and the `substitute()` function. When the | |
357 line starts with `substitute(` this will use the function. Prepend a colon to | |
358 use the command instead: > | |
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359 :substitute(pattern (replacement ( |
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360 |
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361 Note that while variables need to be defined before they can be used, |
21825 | 362 functions can be called before being defined. This is required to allow |
363 for cyclic dependencies between functions. It is slightly less efficient, | |
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364 since the function has to be looked up by name. And a typo in the function |
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365 name will only be found when the function is called. |
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366 |
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367 |
19968 | 368 Omitting function() ~ |
369 | |
370 A user defined function can be used as a function reference in an expression | |
371 without `function()`. The argument types and return type will then be checked. | |
372 The function must already have been defined. > | |
373 | |
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374 var Funcref = MyFunction |
19968 | 375 |
376 When using `function()` the resulting type is "func", a function with any | |
377 number of arguments and any return type. The function can be defined later. | |
378 | |
379 | |
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380 Lambda using => instead of -> ~ |
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381 |
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382 In legacy script there can be confusion between using "->" for a method call |
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383 and for a lambda. Also, when a "{" is found the parser needs to figure out if |
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384 it is the start of a lambda or a dictionary, which is now more complicated |
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385 because of the use of argument types. |
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386 |
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387 To avoid these problems Vim9 script uses a different syntax for a lambda, |
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388 which is similar to Javascript: > |
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389 var Lambda = (arg) => expression |
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390 |
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391 No line break is allowed in the arguments of a lambda up to and including the |
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392 "=>". This is OK: > |
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393 filter(list, (k, v) => |
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394 v > 0) |
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395 This does not work: > |
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396 filter(list, (k, v) |
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397 => v > 0) |
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398 This also does not work: > |
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399 filter(list, (k, |
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400 v) => v > 0) |
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401 But you can use a backslash to concatenate the lines before parsing: > |
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402 filter(list, (k, |
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403 \ v) |
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404 \ => v > 0) |
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405 |
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406 Additionally, a lambda can contain statements in {}: > |
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407 var Lambda = (arg) => { |
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408 g:was_called = 'yes' |
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409 return expression |
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410 } |
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411 NOT IMPLEMENTED YET |
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412 |
23737 | 413 *vim9-curly* |
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414 To avoid the "{" of a dictionary literal to be recognized as a statement block |
24024 | 415 wrap it in parentheses: > |
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416 var Lambda = (arg) => ({key: 42}) |
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417 |
23737 | 418 Also when confused with the start of a command block: > |
419 ({ | |
420 key: value | |
421 })->method() | |
422 | |
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423 |
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424 Automatic line continuation ~ |
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425 |
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426 In many cases it is obvious that an expression continues on the next line. In |
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427 those cases there is no need to prefix the line with a backslash (see |
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428 |line-continuation|). For example, when a list spans multiple lines: > |
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429 var mylist = [ |
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430 'one', |
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431 'two', |
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432 ] |
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433 And when a dict spans multiple lines: > |
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434 var mydict = { |
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435 one: 1, |
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436 two: 2, |
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437 } |
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438 Function call: > |
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439 var result = Func( |
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440 arg1, |
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441 arg2 |
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442 ) |
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443 |
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444 For binary operators in expressions not in [], {} or () a line break is |
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445 possible just before or after the operator. For example: > |
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446 var text = lead |
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447 .. middle |
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448 .. end |
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449 var total = start + |
23573 | 450 end - |
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451 correction |
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452 var result = positive |
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453 ? PosFunc(arg) |
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454 : NegFunc(arg) |
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455 |
21499 | 456 For a method call using "->" and a member using a dot, a line break is allowed |
457 before it: > | |
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458 var result = GetBuilder() |
20965 | 459 ->BuilderSetWidth(333) |
460 ->BuilderSetHeight(777) | |
461 ->BuilderBuild() | |
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462 var result = MyDict |
21499 | 463 .member |
20965 | 464 |
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465 For commands that have an argument that is a list of commands, the | character |
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466 at the start of the line indicates line continuation: > |
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467 autocmd BufNewFile *.match if condition |
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468 | echo 'match' |
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469 | endif |
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470 |
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471 < *E1050* |
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472 To make it possible for the operator at the start of the line to be |
21250 | 473 recognized, it is required to put a colon before a range. This will add |
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474 "start" and print: > |
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475 var result = start |
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476 + print |
21250 | 477 Like this: > |
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478 var result = start + print |
21250 | 479 |
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480 This will assign "start" and print a line: > |
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481 var result = start |
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482 :+ print |
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483 |
23047 | 484 Note that the colon is not required for the |+cmd| argument: > |
485 edit +6 fname | |
486 | |
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487 It is also possible to split a function header over multiple lines, in between |
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488 arguments: > |
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489 def MyFunc( |
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490 text: string, |
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491 separator = '-' |
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492 ): string |
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493 |
23305 | 494 Since a continuation line cannot be easily recognized the parsing of commands |
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495 has been made stricter. E.g., because of the error in the first line, the |
23305 | 496 second line is seen as a separate command: > |
497 popup_create(some invalid expression, { | |
498 exit_cb: Func}) | |
499 Now "exit_cb: Func})" is actually a valid command: save any changes to the | |
500 file "_cb: Func})" and exit. To avoid this kind of mistake in Vim9 script | |
501 there must be white space between most command names and the argument. | |
502 | |
23666 | 503 However, the argument of a command that is a command won't be recognized. For |
504 example, after "windo echo expr" a line break inside "expr" will not be seen. | |
505 | |
23305 | 506 |
21250 | 507 Notes: |
508 - "enddef" cannot be used at the start of a continuation line, it ends the | |
509 current function. | |
510 - No line break is allowed in the LHS of an assignment. Specifically when | |
511 unpacking a list |:let-unpack|. This is OK: > | |
22171 | 512 [var1, var2] = |
21250 | 513 Func() |
514 < This does not work: > | |
22171 | 515 [var1, |
21250 | 516 var2] = |
517 Func() | |
518 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
519 similar commands. This is OK: > | |
22171 | 520 echo [1, |
21250 | 521 2] [3, |
522 4] | |
523 < This does not work: > | |
22171 | 524 echo [1, 2] |
21250 | 525 [3, 4] |
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526 |
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527 No curly braces expansion ~ |
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528 |
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529 |curly-braces-names| cannot be used. |
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530 |
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531 |
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532 Dictionary literals ~ |
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533 |
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534 Traditionally Vim has supported dictionary literals with a {} syntax: > |
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535 let dict = {'key': value} |
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536 |
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537 Later it became clear that using a simple text key is very common, thus |
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538 literal dictionaries were introduced in a backwards compatible way: > |
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539 let dict = #{key: value} |
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540 |
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541 However, this #{} syntax is unlike any existing language. As it turns out |
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542 that using a literal key is much more common than using an expression, and |
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543 considering that JavaScript uses this syntax, using the {} form for dictionary |
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544 literals is considered a much more useful syntax. In Vim9 script the {} form |
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545 uses literal keys: > |
23666 | 546 var dict = {key: value} |
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547 |
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548 This works for alphanumeric characters, underscore and dash. If you want to |
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549 use another character, use a single or double quoted string: > |
23666 | 550 var dict = {'key with space': value} |
551 var dict = {"key\twith\ttabs": value} | |
552 var dict = {'': value} # empty key | |
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553 |
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554 In case the key needs to be an expression, square brackets can be used, just |
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555 like in JavaScript: > |
23666 | 556 var dict = {["key" .. nr]: value} |
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557 |
23827
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558 The key type can be string, number, bool or float. Other types result in an |
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559 error. A number can be given with and without the []: > |
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560 var dict = {123: 'without', [456]: 'with'} |
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561 echo dict |
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562 {'456': 'with', '123': 'without'} |
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563 |
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564 |
23978
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565 No :xit, :t, :k, :append, :change or :insert ~ |
19303 | 566 |
21584
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567 These commands are too easily confused with local variable names. |
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568 Instead of `:x` or `:xit` you can use `:exit`. |
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569 Instead of `:t` you can use `:copy`. |
23978
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570 Instead of `:k` you can use `:mark`. |
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571 |
19303 | 572 |
573 Comparators ~ | |
574 | |
575 The 'ignorecase' option is not used for comparators that use strings. | |
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576 |
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577 |
23666 | 578 For loop ~ |
579 | |
580 Legacy Vim script has some tricks to make a for loop over a list handle | |
581 deleting items at the current or previous item. In Vim9 script it just uses | |
582 the index, if items are deleted then items in the list will be skipped. | |
583 Example legacy script: > | |
584 let l = [1, 2, 3, 4] | |
585 for i in l | |
586 echo i | |
587 call remove(l, index(l, i)) | |
588 endfor | |
589 Would echo: | |
590 1 | |
591 2 | |
592 3 | |
593 4 | |
594 In compiled Vim9 script you get: | |
595 1 | |
596 3 | |
597 Generally, you should not change the list that is iterated over. Make a copy | |
598 first if needed. | |
599 | |
600 | |
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601 White space ~ |
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602 |
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603 Vim9 script enforces proper use of white space. This is no longer allowed: > |
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604 var name=234 # Error! |
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605 var name= 234 # Error! |
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606 var name =234 # Error! |
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607 There must be white space before and after the "=": > |
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608 var name = 234 # OK |
21250 | 609 White space must also be put before the # that starts a comment after a |
610 command: > | |
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611 var name = 234# Error! |
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612 var name = 234 # OK |
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613 |
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614 White space is required around most operators. |
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615 |
23466 | 616 White space is required in a sublist (list slice) around the ":", except at |
617 the start and end: > | |
618 otherlist = mylist[v : count] # v:count has a different meaning | |
619 otherlist = mylist[:] # make a copy of the List | |
620 otherlist = mylist[v :] | |
621 otherlist = mylist[: v] | |
622 | |
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623 White space is not allowed: |
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624 - Between a function name and the "(": > |
23666 | 625 Func (arg) # Error! |
626 Func | |
22171 | 627 \ (arg) # Error! |
23666 | 628 Func |
629 (arg) # Error! | |
630 Func(arg) # OK | |
631 Func( | |
632 arg) # OK | |
633 Func( | |
634 arg # OK | |
635 ) | |
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636 |
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637 |
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638 Conditions and expressions ~ |
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639 |
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640 Conditions and expressions are mostly working like they do in other languages. |
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641 Some values are different from legacy Vim script: |
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642 value legacy Vim script Vim9 script ~ |
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643 0 falsy falsy |
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644 1 truthy truthy |
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645 99 truthy Error! |
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646 "0" falsy Error! |
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647 "99" truthy Error! |
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648 "text" falsy Error! |
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649 |
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650 For the "??" operator and when using "!" then there is no error, every value |
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651 is either falsy or truthy. This is mostly like JavaScript, except that an |
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652 empty list and dict is falsy: |
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653 |
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654 type truthy when ~ |
23466 | 655 bool true, v:true or 1 |
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656 number non-zero |
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657 float non-zero |
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658 string non-empty |
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659 blob non-empty |
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660 list non-empty (different from JavaScript) |
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661 dictionary non-empty (different from JavaScript) |
19968 | 662 func when there is a function name |
23466 | 663 special true or v:true |
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664 job when not NULL |
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665 channel when not NULL |
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666 class when not NULL |
23466 | 667 object when not NULL (TODO: when isTrue() returns true) |
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668 |
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669 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
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670 one: > |
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671 1 || false == true |
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672 0 || 1 == true |
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673 0 || false == false |
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674 1 && true == true |
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675 0 && 1 == false |
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676 8 || 0 Error! |
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677 'yes' && 0 Error! |
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678 [] || 99 Error! |
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679 |
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680 When using "!" for inverting, there is no error for using any type and the |
22500
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681 result is a boolean. "!!" can be used to turn any value into boolean: > |
23573 | 682 !'yes' == false |
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683 !![] == false |
23573 | 684 !![1, 2, 3] == true |
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685 |
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686 When using "`.."` for string concatenation arguments of simple types are |
22500
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687 always converted to string: > |
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688 'hello ' .. 123 == 'hello 123' |
23466 | 689 'hello ' .. v:true == 'hello true' |
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690 |
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691 Simple types are string, float, special and bool. For other types |string()| |
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692 can be used. |
23497
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693 *false* *true* *null* |
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694 In Vim9 script one can use "true" for v:true, "false" for v:false and "null" |
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695 for v:null. When converting a boolean to a string "false" and "true" are |
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696 used, not "v:false" and "v:true" like in legacy script. "v:none" is not |
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697 changed, it is only used in JSON and has no equivalent in other languages. |
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698 |
23666 | 699 Indexing a string with [idx] or [idx : idx] uses character indexes instead of |
21825 | 700 byte indexes. Example: > |
701 echo 'bár'[1] | |
702 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
703 script this results in the string 'á'. | |
23573 | 704 A negative index is counting from the end, "[-1]" is the last character. |
23666 | 705 To exclude the last character use |slice()|. |
23573 | 706 If the index is out of range then an empty string results. |
707 | |
708 In legacy script "++var" and "--var" would be silently accepted and have no | |
709 effect. This is an error in Vim9 script. | |
710 | |
711 Numbers starting with zero are not considered to be octal, only numbers | |
712 starting with "0o" are octal: "0o744". |scriptversion-4| | |
21825 | 713 |
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714 |
21093 | 715 What to watch out for ~ |
716 *vim9-gotchas* | |
717 Vim9 was designed to be closer to often used programming languages, but at the | |
718 same time tries to support the legacy Vim commands. Some compromises had to | |
719 be made. Here is a summary of what might be unexpected. | |
720 | |
721 Ex command ranges need to be prefixed with a colon. > | |
23666 | 722 -> legacy Vim: shifts the previous line to the right |
723 ->func() Vim9: method call in a continuation line | |
724 :-> Vim9: shifts the previous line to the right | |
21093 | 725 |
23666 | 726 %s/a/b legacy Vim: substitute on all lines |
21093 | 727 x = alongname |
23666 | 728 % another Vim9: modulo operator in a continuation line |
729 :%s/a/b Vim9: substitute on all lines | |
730 't legacy Vim: jump to mark t | |
731 'text'->func() Vim9: method call | |
732 :'t Vim9: jump to mark t | |
21093 | 733 |
21676 | 734 Some Ex commands can be confused with assignments in Vim9 script: > |
23666 | 735 g:name = value # assignment |
736 g:pattern:cmd # invalid command - ERROR | |
737 :g:pattern:cmd # :global command | |
21676 | 738 |
21093 | 739 Functions defined with `:def` compile the whole function. Legacy functions |
740 can bail out, and the following lines are not parsed: > | |
741 func Maybe() | |
742 if !has('feature') | |
743 return | |
744 endif | |
745 use-feature | |
746 endfunc | |
747 Vim9 functions are compiled as a whole: > | |
748 def Maybe() | |
749 if !has('feature') | |
750 return | |
751 endif | |
23573 | 752 use-feature # May give a compilation error |
21093 | 753 enddef |
754 For a workaround, split it in two functions: > | |
755 func Maybe() | |
756 if has('feature') | |
23666 | 757 call MaybeInner() |
21093 | 758 endif |
759 endfunc | |
760 if has('feature') | |
761 def MaybeInner() | |
762 use-feature | |
763 enddef | |
764 endif | |
22171 | 765 Or put the unsupported code inside an `if` with a constant expression that |
21991 | 766 evaluates to false: > |
767 def Maybe() | |
768 if has('feature') | |
769 use-feature | |
770 endif | |
771 enddef | |
23573 | 772 < *vim9-user-command* |
23666 | 773 Another side effect of compiling a function is that the presence of a user |
23573 | 774 command is checked at compile time. If the user command is defined later an |
775 error will result. This works: > | |
776 command -nargs=1 MyCommand echom <q-args> | |
777 def Works() | |
778 MyCommand 123 | |
779 enddef | |
780 This will give an error for "MyCommand" not being defined: > | |
781 def Works() | |
782 command -nargs=1 MyCommand echom <q-args> | |
783 MyCommand 123 | |
784 enddef | |
785 A workaround is to invoke the command indirectly with `:execute`: > | |
786 def Works() | |
787 command -nargs=1 MyCommand echom <q-args> | |
788 execute 'MyCommand 123' | |
789 enddef | |
790 | |
21991 | 791 Note that for unrecognized commands there is no check for "|" and a following |
792 command. This will give an error for missing `endif`: > | |
793 def Maybe() | |
794 if has('feature') | use-feature | endif | |
795 enddef | |
21093 | 796 |
23305 | 797 Other differences ~ |
798 | |
799 Patterns are used like 'magic' is set, unless explicitly overruled. | |
800 The 'edcompatible' option value is not used. | |
801 The 'gdefault' option value is not used. | |
802 | |
803 | |
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804 ============================================================================== |
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805 |
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806 3. New style functions *fast-functions* |
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807 |
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808 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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809 |
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810 *:def* |
21825 | 811 :def[!] {name}([arguments])[: {return-type}] |
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812 Define a new function by the name {name}. The body of |
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813 the function follows in the next lines, until the |
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814 matching `:enddef`. |
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815 |
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816 When {return-type} is omitted or is "void" the |
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817 function is not expected to return anything. |
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818 |
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819 {arguments} is a sequence of zero or more argument |
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820 declarations. There are three forms: |
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821 {name}: {type} |
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822 {name} = {value} |
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823 {name}: {type} = {value} |
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824 The first form is a mandatory argument, the caller |
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825 must always provide them. |
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826 The second and third form are optional arguments. |
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827 When the caller omits an argument the {value} is used. |
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828 |
20856 | 829 The function will be compiled into instructions when |
21499 | 830 called, or when `:disassemble` or `:defcompile` is |
831 used. Syntax and type errors will be produced at that | |
832 time. | |
20856 | 833 |
21499 | 834 It is possible to nest `:def` inside another `:def` or |
835 `:function` up to about 50 levels deep. | |
19303 | 836 |
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837 [!] is used as with `:function`. Note that |
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838 script-local functions cannot be deleted or redefined |
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839 later in Vim9 script. They can only be removed by |
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840 reloading the same script. |
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841 |
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842 *:enddef* |
21499 | 843 :enddef End of a function defined with `:def`. It should be on |
844 a line by its own. | |
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845 |
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846 |
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847 If the script the function is defined in is Vim9 script, then script-local |
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848 variables can be accessed without the "s:" prefix. They must be defined |
20856 | 849 before the function is compiled. If the script the function is defined in is |
850 legacy script, then script-local variables must be accessed with the "s:" | |
21991 | 851 prefix and they do not need to exist (they can be deleted any time). |
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852 |
20552 | 853 *:defc* *:defcompile* |
854 :defc[ompile] Compile functions defined in the current script that | |
855 were not compiled yet. | |
856 This will report errors found during the compilation. | |
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857 |
19404 | 858 *:disa* *:disassemble* |
859 :disa[ssemble] {func} Show the instructions generated for {func}. | |
860 This is for debugging and testing. | |
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861 Note that for command line completion of {func} you |
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862 can prepend "s:" to find script-local functions. |
19404 | 863 |
23737 | 864 :disa[ssemble]! {func} Like `:disassemble` but with the instructions used for |
865 profiling. | |
866 | |
21250 | 867 Limitations ~ |
868 | |
869 Local variables will not be visible to string evaluation. For example: > | |
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870 def MapList(): list<string> |
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871 var list = ['aa', 'bb', 'cc', 'dd'] |
21250 | 872 return range(1, 2)->map('list[v:val]') |
873 enddef | |
874 | |
875 The map argument is a string expression, which is evaluated without the | |
876 function scope. Instead, use a lambda: > | |
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877 def MapList(): list<string> |
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878 var list = ['aa', 'bb', 'cc', 'dd'] |
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879 return range(1, 2)->map(( _, v) => list[v]) |
21250 | 880 enddef |
881 | |
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882 The same is true for commands that are not compiled, such as `:global`. |
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883 For these the backtick expansion can be used. Example: > |
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884 def Replace() |
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885 var newText = 'blah' |
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886 g/pattern/s/^/`=newText`/ |
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887 enddef |
21250 | 888 |
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889 ============================================================================== |
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890 |
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891 4. Types *vim9-types* |
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892 |
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893 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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894 |
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895 The following builtin types are supported: |
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896 bool |
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897 number |
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898 float |
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899 string |
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900 blob |
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901 list<{type}> |
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902 dict<{type}> |
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903 job |
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904 channel |
19646 | 905 func |
19968 | 906 func: {type} |
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907 func({type}, ...) |
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908 func({type}, ...): {type} |
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909 |
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910 Not supported yet: |
19904
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911 tuple<a: {type}, b: {type}, ...> |
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912 |
19904
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|
913 These types can be used in declarations, but no value will have this type: |
21499 | 914 {type}|{type} {not implemented yet} |
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915 void |
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916 any |
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917 |
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|
918 There is no array type, use list<{type}> instead. For a list constant an |
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919 efficient implementation is used that avoids allocating lot of small pieces of |
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920 memory. |
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|
921 |
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|
922 A partial and function can be declared in more or less specific ways: |
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|
923 func any kind of function reference, no type |
19968 | 924 checking for arguments or return value |
19904
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|
925 func: {type} any number and type of arguments with specific |
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|
926 return type |
19968 | 927 func({type}) function with argument type, does not return |
19904
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928 a value |
19968 | 929 func({type}): {type} function with argument type and return type |
930 func(?{type}) function with type of optional argument, does | |
931 not return a value | |
932 func(...{type}) function with type of variable number of | |
933 arguments, does not return a value | |
934 func({type}, ?{type}, ...{type}): {type} | |
935 function with: | |
936 - type of mandatory argument | |
937 - type of optional argument | |
938 - type of variable number of arguments | |
939 - return type | |
19904
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940 |
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|
941 If the return type is "void" the function does not return a value. |
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|
942 |
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|
943 The reference can also be a |Partial|, in which case it stores extra arguments |
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|
944 and/or a dictionary, which are not visible to the caller. Since they are |
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|
945 called in the same way the declaration is the same. |
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946 |
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|
947 Custom types can be defined with `:type`: > |
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948 :type MyList list<string> |
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|
949 Custom types must start with a capital letter, to avoid name clashes with |
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|
950 builtin types added later, similarly to user functions. |
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951 {not implemented yet} |
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952 |
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953 And classes and interfaces can be used as types: > |
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954 :class MyClass |
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955 :var mine: MyClass |
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956 |
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957 :interface MyInterface |
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958 :var mine: MyInterface |
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959 |
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960 :class MyTemplate<Targ> |
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961 :var mine: MyTemplate<number> |
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962 :var mine: MyTemplate<string> |
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963 |
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964 :class MyInterface<Targ> |
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965 :var mine: MyInterface<number> |
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966 :var mine: MyInterface<string> |
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967 {not implemented yet} |
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968 |
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969 |
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970 Variable types and type casting ~ |
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971 *variable-types* |
21717
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972 Variables declared in Vim9 script or in a `:def` function have a type, either |
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973 specified explicitly or inferred from the initialization. |
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974 |
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975 Global, buffer, window and tab page variables do not have a specific type, the |
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976 value can be changed at any time, possibly changing the type. Therefore, in |
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977 compiled code the "any" type is assumed. |
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978 |
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|
979 This can be a problem when the "any" type is undesired and the actual type is |
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980 expected to always be the same. For example, when declaring a list: > |
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981 var l: list<number> = [1, g:two] |
23305 | 982 At compile time Vim doesn't know the type of "g:two" and the expression type |
983 becomes list<any>. An instruction is generated to check the list type before | |
984 doing the assignment, which is a bit inefficient. | |
985 *type-casting* | |
986 To avoid this, use a type cast: > | |
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987 var l: list<number> = [1, <number>g:two] |
23305 | 988 The compiled code will then only check that "g:two" is a number and give an |
989 error if it isn't. This is called type casting. | |
21717
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990 |
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991 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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992 after the "<" or before the ">" (to avoid them being confused with |
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993 smaller-than and bigger-than operators). |
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994 |
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995 The semantics is that, if needed, a runtime type check is performed. The |
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996 value is not actually changed. If you need to change the type, e.g. to change |
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997 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
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998 string to a number. |
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999 |
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1000 |
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1001 Type inference ~ |
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1002 *type-inference* |
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1003 In general: Whenever the type is clear it can be omitted. For example, when |
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1004 declaring a variable and giving it a value: > |
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1005 var name = 0 # infers number type |
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1006 var name = 'hello' # infers string type |
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1007 |
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1008 The type of a list and dictionary comes from the common type of the values. |
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1009 If the values all have the same type, that type is used for the list or |
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1010 dictionary. If there is a mix of types, the "any" type is used. > |
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1011 [1, 2, 3] list<number> |
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1012 ['a', 'b', 'c'] list<string> |
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1013 [1, 'x', 3] list<any> |
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1014 |
21991 | 1015 |
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1016 Stricter type checking ~ |
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1017 *type-checking* |
21991 | 1018 In legacy Vim script, where a number was expected, a string would be |
1019 automatically converted to a number. This was convenient for an actual number | |
1020 such as "123", but leads to unexpected problems (but no error message) if the | |
1021 string doesn't start with a number. Quite often this leads to hard-to-find | |
1022 bugs. | |
1023 | |
1024 In Vim9 script this has been made stricter. In most places it works just as | |
22171 | 1025 before, if the value used matches the expected type. There will sometimes be |
1026 an error, thus breaking backwards compatibility. For example: | |
21991 | 1027 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
1028 - Using a string value when setting a number options. | |
1029 - Using a number where a string is expected. *E1024* | |
1030 | |
23573 | 1031 One consequence is that the item type of a list or dict given to map() must |
24024 | 1032 not change. This will give an error in Vim9 script: > |
23573 | 1033 map([1, 2, 3], (i, v) => 'item ' .. i) |
24024 | 1034 E1012: Type mismatch; expected number but got string |
1035 Instead use |mapnew()|. If the item type was determined to be "any" it can | |
1036 change to a more specific type. E.g. when a list of mixed types gets changed | |
1037 to a list of numbers. | |
1038 Same for |extend()|, use |extendnew()| instead, and for |flatten()|, use | |
1039 |flattennew()| instead. | |
23573 | 1040 |
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1041 ============================================================================== |
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1042 |
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1043 5. Namespace, Import and Export |
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1044 *vim9script* *vim9-export* *vim9-import* |
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1045 |
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1046 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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1047 |
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1048 A Vim9 script can be written to be imported. This means that everything in |
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1049 the script is local, unless exported. Those exported items, and only those |
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1050 items, can then be imported in another script. |
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1051 |
21991 | 1052 You can cheat by using the global namespace explicitly. We will assume here |
1053 that you don't do that. | |
1054 | |
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1055 |
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1056 Namespace ~ |
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1057 *vim9-namespace* |
19303 | 1058 To recognize a file that can be imported the `vim9script` statement must |
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1059 appear as the first statement in the file (see |vim9-mix| for an exception). |
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1060 It tells Vim to interpret the script in its own namespace, instead of the |
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1061 global namespace. If a file starts with: > |
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1062 vim9script |
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1063 var myvar = 'yes' |
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1064 Then "myvar" will only exist in this file. While without `vim9script` it would |
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1065 be available as `g:myvar` from any other script and function. |
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1066 |
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1067 The variables at the file level are very much like the script-local "s:" |
20115 | 1068 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
1069 deleted. | |
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1070 |
20115 | 1071 In Vim9 script the global "g:" namespace can still be used as before. And the |
1072 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
1073 declared and they can be deleted. | |
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1074 |
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1075 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
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1076 Vim default value, like with: > |
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1077 :set cpo&vim |
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1078 One of the effects is that |line-continuation| is always enabled. |
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1079 The original value of 'cpoptions' is restored at the end of the script. |
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1080 |
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1081 *vim9-mix* |
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1082 There is one way to use both legacy and Vim9 syntax in one script file: > |
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1083 " comments may go here |
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1084 if !has('vim9script') |
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1085 " legacy script commands go here |
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1086 finish |
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1087 endif |
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1088 vim9script |
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1089 # Vim9 script commands go here |
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1090 This allows for writing a script that takes advantage of the Vim9 script |
24024 | 1091 syntax if possible, but will also work on a Vim version without it. |
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1092 |
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1093 This can only work in two ways: |
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1094 1. The "if" statement evaluates to false, the commands up to `endif` are |
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1095 skipped and `vim9script` is then the first command actually executed. |
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1096 2. The "if" statement evaluates to true, the commands up to `endif` are |
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1097 executed and `finish` bails out before reaching `vim9script`. |
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1098 |
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1099 TODO: The "vim9script" feature does not exist yet, it will only be added once |
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1100 the Vim9 script syntax has been fully implemented. |
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1101 |
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1102 |
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1103 Export ~ |
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1104 *:export* *:exp* |
21499 | 1105 Exporting an item can be written as: > |
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1106 export const EXPORTED_CONST = 1234 |
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1107 export var someValue = ... |
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1108 export final someValue = ... |
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1109 export const someValue = ... |
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1110 export def MyFunc() ... |
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1111 export class MyClass ... |
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1112 |
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1113 As this suggests, only constants, variables, `:def` functions and classes can |
21499 | 1114 be exported. {classes are not implemented yet} |
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1115 |
20856 | 1116 *E1042* |
1117 `:export` can only be used in Vim9 script, at the script level. | |
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1118 |
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1119 |
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1120 Import ~ |
20965 | 1121 *:import* *:imp* *E1094* |
19181
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1122 The exported items can be imported individually in another Vim9 script: > |
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1123 import EXPORTED_CONST from "thatscript.vim" |
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1124 import MyClass from "myclass.vim" |
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1125 |
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1126 To import multiple items at the same time: > |
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1127 import {someValue, MyClass} from "thatscript.vim" |
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1128 |
19303 | 1129 In case the name is ambiguous, another name can be specified: > |
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1130 import MyClass as ThatClass from "myclass.vim" |
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1131 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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1132 |
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1133 To import all exported items under a specific identifier: > |
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1134 import * as That from 'thatscript.vim' |
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1135 |
22328 | 1136 {not implemented yet: using "This as That"} |
1137 | |
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1138 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
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1139 to choose the name "That", but it is highly recommended to use the name of the |
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1140 script file to avoid confusion. |
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1141 |
22171 | 1142 `:import` can also be used in legacy Vim script. The imported items still |
1143 become script-local, even when the "s:" prefix is not given. | |
1144 | |
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1145 The script name after `import` can be: |
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1146 - A relative path, starting "." or "..". This finds a file relative to the |
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1147 location of the script file itself. This is useful to split up a large |
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1148 plugin into several files. |
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1149 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
22723 | 1150 will rarely be used. |
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1151 - A path not being relative or absolute. This will be found in the |
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1152 "import" subdirectories of 'runtimepath' entries. The name will usually be |
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1153 longer and unique, to avoid loading the wrong file. |
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1154 |
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1155 Once a vim9 script file has been imported, the result is cached and used the |
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1156 next time the same script is imported. It will not be read again. |
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1157 *:import-cycle* |
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1158 The `import` commands are executed when encountered. If that script (directly |
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1159 or indirectly) imports the current script, then items defined after the |
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1160 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
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1161 result in undefined items. |
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1162 |
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1163 |
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1164 Import in an autoload script ~ |
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1165 |
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1166 For optimal startup speed, loading scripts should be postponed until they are |
19303 | 1167 actually needed. A recommended mechanism: |
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1168 |
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1169 1. In the plugin define user commands, functions and/or mappings that refer to |
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1170 an autoload script. > |
23666 | 1171 command -nargs=1 SearchForStuff searchfor#Stuff(<f-args>) |
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1172 |
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1173 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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1174 |
21825 | 1175 2. In the autoload script do the actual work. You can import items from |
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1176 other files to split up functionality in appropriate pieces. > |
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1177 vim9script |
23573 | 1178 import FilterFunc from "../import/someother.vim" |
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1179 def searchfor#Stuff(arg: string) |
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1180 var filtered = FilterFunc(arg) |
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1181 ... |
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1182 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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1183 must be exactly the same as the prefix for the function name, that is how |
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1184 Vim finds the file. |
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1185 |
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1186 3. Other functionality, possibly shared between plugins, contains the exported |
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1187 items and any private items. > |
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1188 vim9script |
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1189 var localVar = 'local' |
22171 | 1190 export def FilterFunc(arg: string): string |
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1191 ... |
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1192 < This goes in .../import/someother.vim. |
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1193 |
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1194 When compiling a `:def` function and a function in an autoload script is |
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1195 encountered, the script is not loaded until the `:def` function is called. |
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1196 |
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1197 |
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1198 Import in legacy Vim script ~ |
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1199 |
20856 | 1200 If an `import` statement is used in legacy Vim script, the script-local "s:" |
1201 namespace will be used for the imported item, even when "s:" is not specified. | |
19181
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1202 |
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1203 |
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1204 ============================================================================== |
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1205 |
22328 | 1206 6. Future work: classes *vim9-classes* |
1207 | |
1208 Above "class" was mentioned a few times, but it has not been implemented yet. | |
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1209 Most of Vim9 script can be created without this functionality, and since |
22328 | 1210 implementing classes is going to be a lot of work, it is left for the future. |
1211 For now we'll just make sure classes can be added later. | |
1212 | |
1213 Thoughts: | |
1214 - `class` / `endclass`, everything in one file | |
1215 - Class names are always CamelCase | |
1216 - Single constructor | |
1217 - Single inheritance with `class ThisClass extends BaseClass` | |
1218 - `abstract class` | |
1219 - `interface` (Abstract class without any implementation) | |
1220 - `class SomeClass implements SomeInterface` | |
1221 - Generics for class: `class <Tkey, Tentry>` | |
1222 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
1223 | |
1224 Again, much of this is from TypeScript. | |
1225 | |
1226 Some things that look like good additions: | |
1227 - Use a class as an interface (like Dart) | |
1228 - Extend a class with methods, using an import (like Dart) | |
1229 | |
1230 An important class that will be provided is "Promise". Since Vim is single | |
1231 threaded, connecting asynchronous operations is a natural way of allowing | |
1232 plugins to do their work without blocking the user. It's a uniform way to | |
1233 invoke callbacks and handle timeouts and errors. | |
1234 | |
1235 ============================================================================== | |
1236 | |
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1237 9. Rationale *vim9-rationale* |
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1238 |
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1239 The :def command ~ |
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1240 |
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1241 Plugin writers have asked for much faster Vim script. Investigations have |
19303 | 1242 shown that keeping the existing semantics of function calls make this close to |
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1243 impossible, because of the overhead involved with calling a function, setting |
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1244 up the local function scope and executing lines. There are many details that |
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1245 need to be handled, such as error messages and exceptions. The need to create |
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1246 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1247 much overhead that cannot be avoided. |
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1248 |
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1249 Therefore the `:def` method to define a new-style function had to be added, |
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1250 which allows for a function with different semantics. Most things still work |
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1251 as before, but some parts do not. A new way to define a function was |
22391
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1252 considered the best way to separate the legacy style code from Vim9 style code. |
19181
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1253 |
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1254 Using "def" to define a function comes from Python. Other languages use |
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1255 "function" which clashes with legacy Vim script. |
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1256 |
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1257 |
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1258 Type checking ~ |
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1259 |
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1260 When compiling lines of Vim commands into instructions as much as possible |
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1261 should be done at compile time. Postponing it to runtime makes the execution |
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1262 slower and means mistakes are found only later. For example, when |
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1263 encountering the "+" character and compiling this into a generic add |
23666 | 1264 instruction, at runtime the instruction would have to inspect the type of the |
1265 arguments and decide what kind of addition to do. And when the type is | |
1266 dictionary throw an error. If the types are known to be numbers then an "add | |
1267 number" instruction can be used, which is faster. The error can be given at | |
1268 compile time, no error handling is needed at runtime, since adding two numbers | |
1269 cannot fail. | |
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1270 |
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1271 The syntax for types, using <type> for compound types, is similar to Java. It |
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1272 is easy to understand and widely used. The type names are what were used in |
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1273 Vim before, with some additions such as "void" and "bool". |
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1274 |
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1275 |
22328 | 1276 Removing clutter and weirdness ~ |
20856 | 1277 |
22328 | 1278 Once decided that `:def` functions have different syntax than legacy functions, |
1279 we are free to add improvements to make the code more familiar for users who | |
1280 know popular programming languages. In other words: remove weird things that | |
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1281 only Vim does. |
22328 | 1282 |
1283 We can also remove clutter, mainly things that were done to make Vim script | |
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1284 backwards compatible with the good old Vi commands. |
20856 | 1285 |
22328 | 1286 Examples: |
1287 - Drop `:call` for calling a function and `:eval` for manipulating data. | |
1288 - Drop using a leading backslash for line continuation, automatically figure | |
1289 out where an expression ends. | |
20856 | 1290 |
22328 | 1291 However, this does require that some things need to change: |
1292 - Comments start with # instead of ", to avoid confusing them with strings. | |
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1293 This is good anyway, it is known from several popular languages. |
22328 | 1294 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
1295 expressions (single quote can be a string or a mark, "/" can be divide or a | |
1296 search command, etc.). | |
1297 | |
1298 Goal is to limit the differences. A good criteria is that when the old syntax | |
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1299 is accidentally used you are very likely to get an error message. |
20856 | 1300 |
1301 | |
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1302 Syntax and semantics from popular languages ~ |
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1303 |
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1304 Script writers have complained that the Vim script syntax is unexpectedly |
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1305 different from what they are used to. To reduce this complaint popular |
20856 | 1306 languages are used as an example. At the same time, we do not want to abandon |
1307 the well-known parts of legacy Vim script. | |
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1308 |
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1309 For many things TypeScript is followed. It's a recent language that is |
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1310 gaining popularity and has similarities with Vim script. It also has a |
22328 | 1311 mix of static typing (a variable always has a known value type) and dynamic |
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1312 typing (a variable can have different types, this changes at runtime). Since |
22328 | 1313 legacy Vim script is dynamically typed and a lot of existing functionality |
1314 (esp. builtin functions) depends on that, while static typing allows for much | |
1315 faster execution, we need to have this mix in Vim9 script. | |
1316 | |
22171 | 1317 There is no intention to completely match TypeScript syntax and semantics. We |
1318 just want to take those parts that we can use for Vim and we expect Vim users | |
22328 | 1319 will be happy with. TypeScript is a complex language with its own history, |
1320 advantages and disadvantages. To get an idea of the disadvantages read the | |
1321 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
22272
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1322 parts" and read the "Things to avoid" section. |
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1323 |
22328 | 1324 People familiar with other languages (Java, Python, etc.) will also find |
1325 things in TypeScript that they do not like or do not understand. We'll try to | |
1326 avoid those things. | |
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1327 |
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1328 Specific items from TypeScript we avoid: |
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1329 - Overloading "+", using it both for addition and string concatenation. This |
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1330 goes against legacy Vim script and often leads to mistakes. For that reason |
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1331 we will keep using ".." for string concatenation. Lua also uses ".." this |
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1332 way. And it allows for conversion to string for more values. |
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1333 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
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1334 cannot assign the value to a boolean. That is inconsistent and can be |
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1335 annoying. Vim recognizes an expression with && or || and allows using the |
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1336 result as a bool. TODO: to be reconsidered |
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1337 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
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1338 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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1339 Falsy. |
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1340 - TypeScript has various "Readonly" types, which have limited usefulness, |
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1341 since a type cast can remove the immutable nature. Vim locks the value, |
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1342 which is more flexible, but is only checked at runtime. |
22171 | 1343 |
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1344 |
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1345 Declarations ~ |
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1346 |
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1347 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
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1348 are used. That is different, thus it's good to use a different command: |
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1349 `:var`. This is used in many languages. The semantics might be slightly |
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1350 different, but it's easily recognized as a declaration. |
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1351 |
23047 | 1352 Using `:const` for constants is common, but the semantics varies. Some |
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1353 languages only make the variable immutable, others also make the value |
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1354 immutable. Since "final" is well known from Java for only making the variable |
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1355 immutable we decided to use that. And then `:const` can be used for making |
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1356 both immutable. This was also used in legacy Vim script and the meaning is |
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1357 almost the same. |
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1358 |
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1359 What we end up with is very similar to Dart: > |
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1360 :var name # mutable variable and value |
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1361 :final name # immutable variable, mutable value |
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1362 :const name # immutable variable and value |
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1363 |
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1364 Since legacy and Vim9 script will be mixed and global variables will be |
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1365 shared, optional type checking is desirable. Also, type inference will avoid |
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1366 the need for specifying the type in many cases. The TypeScript syntax fits |
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1367 best for adding types to declarations: > |
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1368 var name: string # string type is specified |
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1369 ... |
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1370 name = 'John' |
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1371 const greeting = 'hello' # string type is inferred |
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1372 |
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1373 This is how we put types in a declaration: > |
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1374 var mylist: list<string> |
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1375 final mylist: list<string> = ['foo'] |
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1376 def Func(arg1: number, arg2: string): bool |
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1377 |
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1378 Two alternatives were considered: |
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1379 1. Put the type before the name, like Dart: > |
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1380 var list<string> mylist |
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1381 final list<string> mylist = ['foo'] |
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1382 def Func(number arg1, string arg2) bool |
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1383 2. Put the type after the variable name, but do not use a colon, like Go: > |
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1384 var mylist list<string> |
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1385 final mylist list<string> = ['foo'] |
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1386 def Func(arg1 number, arg2 string) bool |
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1387 |
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1388 The first is more familiar for anyone used to C or Java. The second one |
22565 | 1389 doesn't really have an advantage over the first, so let's discard the second. |
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1390 |
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1391 Since we use type inference the type can be left out when it can be inferred |
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1392 from the value. This means that after `var` we don't know if a type or a name |
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1393 follows. That makes parsing harder, not only for Vim but also for humans. |
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1394 Also, it will not be allowed to use a variable name that could be a type name, |
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1395 using `var string string` is too confusing. |
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1396 |
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1397 The chosen syntax, using a colon to separate the name from the type, adds |
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1398 punctuation, but it actually makes it easier to recognize the parts of a |
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1399 declaration. |
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1400 |
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1401 |
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1402 Expressions ~ |
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1403 |
22565 | 1404 Expression evaluation was already close to what other languages are doing. |
1405 Some details are unexpected and can be improved. For example a boolean | |
1406 condition would accept a string, convert it to a number and check if the | |
1407 number is non-zero. This is unexpected and often leads to mistakes, since | |
1408 text not starting with a number would be converted to zero, which is | |
22723 | 1409 considered false. Thus using a string for a condition would often not give an |
1410 error and be considered false. That is confusing. | |
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1411 |
23047 | 1412 In Vim9 type checking is stricter to avoid mistakes. Where a condition is |
22565 | 1413 used, e.g. with the `:if` command and the `||` operator, only boolean-like |
1414 values are accepted: | |
1415 true: `true`, `v:true`, `1`, `0 < 9` | |
1416 false: `false`, `v:false`, `0`, `0 > 9` | |
1417 Note that the number zero is false and the number one is true. This is more | |
22723 | 1418 permissive than most other languages. It was done because many builtin |
22565 | 1419 functions return these values. |
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1420 |
22565 | 1421 If you have any type of value and want to use it as a boolean, use the `!!` |
1422 operator: | |
1423 true: !`!'text'`, `!![99]`, `!!{'x': 1}`, `!!99` | |
1424 false: `!!''`, `!![]`, `!!{}` | |
1425 | |
1426 From a language like JavaScript we have this handy construct: > | |
1427 GetName() || 'unknown' | |
1428 However, this conflicts with only allowing a boolean for a condition. | |
1429 Therefore the "??" operator was added: > | |
1430 GetName() ?? 'unknown' | |
1431 Here you can explicitly express your intention to use the value as-is and not | |
1432 result in a boolean. This is called the |falsy-operator|. | |
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1433 |
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1434 |
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1435 Import and Export ~ |
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1436 |
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1437 A problem of legacy Vim script is that by default all functions and variables |
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1438 are global. It is possible to make them script-local, but then they are not |
22171 | 1439 available in other scripts. This defies the concept of a package that only |
1440 exports selected items and keeps the rest local. | |
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1441 |
21825 | 1442 In Vim9 script a mechanism very similar to the JavaScript import and export |
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1443 mechanism is supported. It is a variant to the existing `:source` command |
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1444 that works like one would expect: |
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1445 - Instead of making everything global by default, everything is script-local, |
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1446 unless exported. |
22171 | 1447 - When importing a script the symbols that are imported are explicitly listed, |
1448 avoiding name conflicts and failures if functionality is added later. | |
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1449 - The mechanism allows for writing a big, long script with a very clear API: |
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1450 the exported function(s) and class(es). |
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1451 - By using relative paths loading can be much faster for an import inside of a |
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1452 package, no need to search many directories. |
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1453 - Once an import has been used, it can be cached and loading it again can be |
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1454 avoided. |
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1455 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1456 |
20856 | 1457 When sourcing a Vim9 script from a legacy script, only the items defined |
1458 globally can be used, not the exported items. Alternatives considered: | |
1459 - All the exported items become available as script-local items. This makes | |
22171 | 1460 it uncontrollable what items get defined and likely soon leads to trouble. |
20856 | 1461 - Use the exported items and make them global. Disadvantage is that it's then |
1462 not possible to avoid name clashes in the global namespace. | |
1463 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
1464 makes it difficult to use scripts for testing, or sourcing them from the | |
1465 command line to try them out. | |
22171 | 1466 Note that you can also use `:import` in legacy Vim script, see above. |
20856 | 1467 |
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1468 |
22328 | 1469 Compiling functions early ~ |
1470 | |
1471 Functions are compiled when called or when `:defcompile` is used. Why not | |
1472 compile them early, so that syntax and type errors are reported early? | |
1473 | |
1474 The functions can't be compiled right away when encountered, because there may | |
1475 be forward references to functions defined later. Consider defining functions | |
1476 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
1477 to reorder the functions to avoid forward references. | |
1478 | |
1479 An alternative would be to first scan through the file to locate items and | |
1480 figure out their type, so that forward references are found, and only then | |
1481 execute the script and compile the functions. This means the script has to be | |
1482 parsed twice, which is slower, and some conditions at the script level, such | |
1483 as checking if a feature is supported, are hard to use. An attempt was made | |
1484 to see if it works, but it turned out to be impossible to make work nicely. | |
1485 | |
1486 It would be possible to compile all the functions at the end of the script. | |
1487 The drawback is that if a function never gets called, the overhead of | |
1488 compiling it counts anyway. Since startup speed is very important, in most | |
1489 cases it's better to do it later and accept that syntax and type errors are | |
1490 only reported then. In case these errors should be found early, e.g. when | |
1491 testing, the `:defcompile` command will help out. | |
1492 | |
1493 | |
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1494 Why not use an embedded language? ~ |
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1495 |
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1496 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
22328 | 1497 these interfaces have never become widely used, for various reasons. When |
1498 Vim9 was designed a decision was made to make these interfaces lower priority | |
1499 and concentrate on Vim script. | |
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1500 |
22328 | 1501 Still, plugin writers may find other languages more familiar, want to use |
1502 existing libraries or see a performance benefit. We encourage plugin authors | |
1503 to write code in any language and run it as an external tool, using jobs and | |
1504 channels. We can try to make this easier somehow. | |
1505 | |
1506 Using an external tool also has disadvantages. An alternative is to convert | |
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1507 the tool into Vim script. For that to be possible without too much |
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1508 translation, and keeping the code fast at the same time, the constructs of the |
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1509 tool need to be supported. Since most languages support classes the lack of |
22171 | 1510 support for classes in Vim is then a problem. |
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1511 |
22328 | 1512 |
1513 Classes ~ | |
1514 | |
1515 Vim supports a kind-of object oriented programming by adding methods to a | |
1516 dictionary. With some care this can be made to work, but it does not look | |
1517 like real classes. On top of that, it's quite slow, because of the use of | |
1518 dictionaries. | |
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1519 |
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1520 The support of classes in Vim9 script is a "minimal common functionality" of |
22171 | 1521 class support in most languages. It works much like Java, which is the most |
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1522 popular programming language. |
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1523 |
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1524 |
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1525 |
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1526 vim:tw=78:ts=8:noet:ft=help:norl: |