Mercurial > vim
annotate runtime/doc/vim9.txt @ 22920:696364caabea v8.2.2007
patch 8.2.2007: test for insert mode in popup is not reliable
Commit: https://github.com/vim/vim/commit/17ab28daa060c3c263841329e74befb9c6e8b588
Author: Bram Moolenaar <Bram@vim.org>
Date: Wed Nov 18 12:24:01 2020 +0100
patch 8.2.2007: test for insert mode in popup is not reliable
Problem: Test for insert mode in popup is not reliable.
Solution: Wait for the popup to disappear. (Ozaki Kiichi, closes https://github.com/vim/vim/issues/7321)
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Wed, 18 Nov 2020 12:30:03 +0100 |
| parents | 5b7ea82bc18f |
| children | 00b0275ffe7f |
| rev | line source |
|---|---|
| 22723 | 1 *vim9.txt* For Vim version 8.2. Last change: 2020 Oct 17 |
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4 VIM REFERENCE MANUAL by Bram Moolenaar |
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6 |
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7 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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8 |
| 20241 | 9 Vim9 script commands and expressions. *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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15 |
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16 |
| 21676 | 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 |
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55 When using `:function` in a Vim9 script file the legacy syntax is used. |
| 20241 | 56 However, this can be confusing and is therefore discouraged. |
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57 |
| 20241 | 58 Vim9 script and legacy Vim script can be mixed. There is no requirement to |
| 22328 | 59 rewrite old scripts, they keep working as before. You may want to use a few |
| 60 `:def` functions for code that needs to be fast. | |
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61 |
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62 ============================================================================== |
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63 |
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64 2. Differences from legacy Vim script *vim9-differences* |
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65 |
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66 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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67 |
| 22441 | 68 Overview ~ |
| 69 | |
| 70 Brief summary of the differences you will most often encounter when using Vim9 | |
| 71 script and `:def` functions; details are below: | |
| 72 - Comments start with #, not ": > | |
| 73 echo "hello" # comment | |
| 74 - Using a backslash for line continuation is hardly ever needed: > | |
| 75 echo "hello " | |
| 76 .. yourName | |
| 77 .. ", how are you?" | |
| 78 - White space is required in many places. | |
| 79 - Assign values without `:let`, declare variables with `:var`: > | |
| 80 var count = 0 | |
| 81 count += 3 | |
| 82 - Constants can be declared with `:final` and `:const`: > | |
| 83 final matches = [] # add matches | |
| 84 const names = ['Betty', 'Peter'] # cannot be changed | |
| 85 - `:final` cannot be used as an abbreviation of `:finally`. | |
| 86 - Variables and functions are script-local by default. | |
| 87 - Functions are declared with argument types and return type: > | |
| 88 def CallMe(count: number, message: string): bool | |
| 89 - Call functions without `:call`: > | |
| 90 writefile(['done'], 'file.txt') | |
| 91 - You cannot use `:xit`, `:t`, `:append`, `:change`, `:insert` or curly-braces | |
| 92 names. | |
| 93 - A range before a command must be prefixed with a colon: > | |
| 94 :%s/this/that | |
| 95 | |
| 96 | |
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97 Comments starting with # ~ |
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98 |
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99 In legacy Vim script comments start with double quote. In Vim9 script |
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100 comments start with #. > |
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101 # declarations |
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102 var count = 0 # number of occurrences |
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103 |
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104 The reason is that a double quote can also be the start of a string. In many |
| 21825 | 105 places, especially halfway through an expression with a line break, it's hard |
| 106 to tell what the meaning is, since both a string and a comment can be followed | |
| 107 by arbitrary text. To avoid confusion only # comments are recognized. This | |
| 108 is the same as in shell scripts and Python programs. | |
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109 |
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110 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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111 `:number` for that. > |
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112 101 number |
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113 |
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114 To improve readability there must be a space between a command and the # |
| 20115 | 115 that starts a comment. Note that #{ is the start of a dictionary, therefore |
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116 it does not start a comment. |
| 20115 | 117 |
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118 |
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119 Vim9 functions ~ |
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120 |
| 20241 | 121 A function defined with `:def` is compiled. Execution is many times faster, |
| 122 often 10x to 100x times. | |
| 123 | |
| 20552 | 124 Many errors are already found when compiling, before the function is executed. |
| 20241 | 125 The syntax is strict, to enforce code that is easy to read and understand. |
| 126 | |
| 21991 | 127 Compilation is done when: |
| 128 - the function is first called | |
| 129 - when the `:defcompile` command is encountered in the script where the | |
| 130 function was defined | |
| 131 - `:disassemble` is used for the function. | |
| 132 - a function that is compiled calls the function or uses it as a function | |
| 133 reference | |
| 20552 | 134 |
| 135 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
| 136 "closure". A `:def` function always aborts on an error, does not get a range | |
| 137 passed and cannot be a "dict" function. | |
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138 |
| 20241 | 139 The argument types and return type need to be specified. The "any" type can |
| 140 be used, type checking will then be done at runtime, like with legacy | |
| 141 functions. | |
| 142 | |
| 21825 | 143 Arguments are accessed by name, without "a:", just like any other language. |
| 144 There is no "a:" dictionary or "a:000" list. | |
| 20241 | 145 |
| 146 Variable arguments are defined as the last argument, with a name and have a | |
| 21825 | 147 list type, similar to TypeScript. For example, a list of numbers: > |
| 22171 | 148 def MyFunc(...itemlist: list<number>) |
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149 for item in itemlist |
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150 ... |
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151 |
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152 |
| 20241 | 153 Functions and variables are script-local by default ~ |
| 20856 | 154 *vim9-scopes* |
| 20115 | 155 When using `:function` or `:def` to specify a new function at the script level |
| 156 in a Vim9 script, the function is local to the script, as if "s:" was | |
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157 prefixed. Using the "s:" prefix is optional. To define a global function or |
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158 variable the "g:" prefix must be used. For functions in an autoload script |
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159 the "name#" prefix is sufficient. > |
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160 def ThisFunction() # script-local |
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161 def s:ThisFunction() # script-local |
| 22171 | 162 def g:ThatFunction() # global |
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163 def scriptname#function() # autoload |
| 20115 | 164 |
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165 When using `:function` or `:def` to specify a nested function inside a `:def` |
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166 function, this nested function is local to the code block it is defined in. |
| 22565 | 167 In a `:def` function it is not possible to define a script-local function. It |
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168 is possible to define a global function by using the "g:" prefix. |
| 20115 | 169 |
| 170 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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171 search for the function: |
| 22565 | 172 - in the function scope, in block scopes |
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173 - in the script scope, possibly imported |
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174 - in the list of global functions |
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175 However, it is recommended to always use "g:" to refer to a global function |
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176 for clarity. |
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177 |
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178 In all cases the function must be defined before used. That is when it is |
| 22723 | 179 called, when `:defcompile` causes it to be compiled, or when code that calls |
| 180 it is being compiled (to figure out the return type). | |
| 20241 | 181 |
| 21676 | 182 The result is that functions and variables without a namespace can usually be |
| 20241 | 183 found in the script, either defined there or imported. Global functions and |
| 21676 | 184 variables could be defined anywhere (good luck finding out where!). |
| 20115 | 185 |
| 21825 | 186 Global functions can still be defined and deleted at nearly any time. In |
| 20317 | 187 Vim9 script script-local functions are defined once when the script is sourced |
| 20552 | 188 and cannot be deleted or replaced. |
| 20115 | 189 |
| 190 | |
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191 Variable declarations with :var, :final and :const ~ |
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192 *vim9-declaration* *:var* |
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193 Local variables need to be declared with `:var`. Local constants need to be |
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194 declared with `:final` or `:const`. We refer to both as "variables" in this |
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195 section. |
|
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196 |
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197 Variables can be local to a script, function or code block: > |
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198 vim9script |
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199 var script_var = 123 |
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200 def SomeFunc() |
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201 var func_var = script_var |
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202 if cond |
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203 var block_var = func_var |
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204 ... |
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205 |
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206 The variables are only visible in the block where they are defined and nested |
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207 blocks. Once the block ends the variable is no longer accessible: > |
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208 if cond |
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209 var inner = 5 |
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210 else |
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211 var inner = 0 |
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212 endif |
| 22171 | 213 echo inner # Error! |
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214 |
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215 The declaration must be done earlier: > |
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216 var inner: number |
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217 if cond |
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218 inner = 5 |
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219 else |
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220 inner = 0 |
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221 endif |
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222 echo inner |
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223 |
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224 To intentionally hide a variable from code that follows, a block can be |
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225 used: > |
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226 { |
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227 var temp = 'temp' |
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228 ... |
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229 } |
| 22171 | 230 echo temp # Error! |
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231 |
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232 Declaring a variable with a type but without an initializer will initialize to |
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233 zero, false or empty. |
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234 |
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235 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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236 without any command. The same for global, window, tab, buffer and Vim |
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237 variables, because they are not really declared. They can also be deleted |
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238 with `:unlet`. |
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239 |
| 21676 | 240 Variables and functions cannot shadow previously defined or imported variables |
| 241 and functions. | |
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242 Variables may shadow Ex commands, rename the variable if needed. |
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243 |
| 20241 | 244 Global variables and user defined functions must be prefixed with "g:", also |
| 245 at the script level. > | |
| 19968 | 246 vim9script |
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247 var script_local = 'text' |
| 21499 | 248 g:global = 'value' |
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249 var Funcref = g:ThatFunction |
| 19968 | 250 |
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251 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
|
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252 used to repeat a `:substitute` command. |
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253 |
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254 |
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255 Constants ~ |
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256 *vim9-const* *vim9-final* |
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257 How constants work varies between languages. Some consider a variable that |
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258 can't be assigned another value a constant. JavaScript is an example. Others |
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259 also make the value immutable, thus when a constant uses a list, the list |
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260 cannot be changed. In Vim9 we can use both. |
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261 |
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262 `:const` is used for making both the variable and the value a constant. Use |
|
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263 this for composite structures that you want to make sure will not be modified. |
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264 Example: > |
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265 const myList = [1, 2] |
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266 myList = [3, 4] # Error! |
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267 myList[0] = 9 # Error! |
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268 muList->add(3) # Error! |
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269 < *:final* |
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270 `:final` is used for making only the variable a constant, the value can be |
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271 changed. This is well known from Java. Example: > |
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272 final myList = [1, 2] |
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273 myList = [3, 4] # Error! |
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274 myList[0] = 9 # OK |
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275 muList->add(3) # OK |
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276 |
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277 It is common to write constants as ALL_CAPS, but you don't have to. |
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278 |
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279 The constant only applies to the value itself, not what it refers to. > |
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280 final females = ["Mary"] |
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281 const NAMES = [["John", "Peter"], females] |
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282 NAMES[0] = ["Jack"] # Error! |
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283 NAMES[0][0] = "Jack" # Error! |
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284 NAMES[1] = ["Emma"] # Error! |
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285 Names[1][0] = "Emma" # OK, now females[0] == "Emma" |
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286 |
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287 < *E1092* |
| 21499 | 288 Declaring more than one variable at a time, using the unpack notation, is |
| 289 currently not supported: > | |
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290 var [v1, v2] = GetValues() # Error! |
| 21499 | 291 That is because the type needs to be inferred from the list item type, which |
| 292 isn't that easy. | |
| 293 | |
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294 |
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295 Omitting :call and :eval ~ |
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296 |
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297 Functions can be called without `:call`: > |
| 22171 | 298 writefile(lines, 'file') |
| 19303 | 299 Using `:call` is still possible, but this is discouraged. |
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300 |
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301 A method call without `eval` is possible, so long as the start is an |
|
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302 identifier or can't be an Ex command. Examples: > |
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303 myList->add(123) |
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304 g:myList->add(123) |
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305 [1, 2, 3]->Process() |
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306 #{a: 1, b: 2}->Process() |
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307 {'a': 1, 'b': 2}->Process() |
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308 "foobar"->Process() |
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309 ("foobar")->Process() |
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310 'foobar'->Process() |
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311 ('foobar')->Process() |
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312 |
| 21825 | 313 In the rare case there is ambiguity between a function name and an Ex command, |
| 21676 | 314 prepend ":" to make clear you want to use the Ex command. For example, there |
| 315 is both the `:substitute` command and the `substitute()` function. When the | |
| 316 line starts with `substitute(` this will use the function. Prepend a colon to | |
| 317 use the command instead: > | |
|
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318 :substitute(pattern (replacement ( |
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319 |
|
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320 Note that while variables need to be defined before they can be used, |
| 21825 | 321 functions can be called before being defined. This is required to allow |
| 322 for cyclic dependencies between functions. It is slightly less efficient, | |
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323 since the function has to be looked up by name. And a typo in the function |
|
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324 name will only be found when the function is called. |
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325 |
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326 |
| 19968 | 327 Omitting function() ~ |
| 328 | |
| 329 A user defined function can be used as a function reference in an expression | |
| 330 without `function()`. The argument types and return type will then be checked. | |
| 331 The function must already have been defined. > | |
| 332 | |
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333 var Funcref = MyFunction |
| 19968 | 334 |
| 335 When using `function()` the resulting type is "func", a function with any | |
| 336 number of arguments and any return type. The function can be defined later. | |
| 337 | |
| 338 | |
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339 Automatic line continuation ~ |
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340 |
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341 In many cases it is obvious that an expression continues on the next line. In |
| 21676 | 342 those cases there is no need to prefix the line with a backslash |
| 343 |line-continuation|. For example, when a list spans multiple lines: > | |
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344 var mylist = [ |
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345 'one', |
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346 'two', |
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347 ] |
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348 And when a dict spans multiple lines: > |
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349 var mydict = #{ |
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350 one: 1, |
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351 two: 2, |
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352 } |
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353 Function call: > |
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354 var result = Func( |
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355 arg1, |
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356 arg2 |
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357 ) |
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358 |
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359 For binary operators in expressions not in [], {} or () a line break is |
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360 possible just before or after the operator. For example: > |
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361 var text = lead |
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362 .. middle |
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363 .. end |
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364 var total = start + |
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365 end - |
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366 correction |
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367 var result = positive |
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368 ? PosFunc(arg) |
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369 : NegFunc(arg) |
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370 |
| 21499 | 371 For a method call using "->" and a member using a dot, a line break is allowed |
| 372 before it: > | |
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373 var result = GetBuilder() |
| 20965 | 374 ->BuilderSetWidth(333) |
| 375 ->BuilderSetHeight(777) | |
| 376 ->BuilderBuild() | |
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377 var result = MyDict |
| 21499 | 378 .member |
| 20965 | 379 |
|
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380 < *E1050* |
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381 To make it possible for the operator at the start of the line to be |
| 21250 | 382 recognized, it is required to put a colon before a range. This will add |
|
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383 "start" and print: > |
|
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384 var result = start |
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385 + print |
| 21250 | 386 Like this: > |
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387 var result = start + print |
| 21250 | 388 |
|
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389 This will assign "start" and print a line: > |
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390 var result = start |
|
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391 :+ print |
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392 |
|
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393 It is also possible to split a function header over multiple lines, in between |
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394 arguments: > |
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395 def MyFunc( |
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396 text: string, |
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397 separator = '-' |
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398 ): string |
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399 |
| 21250 | 400 Notes: |
| 401 - "enddef" cannot be used at the start of a continuation line, it ends the | |
| 402 current function. | |
| 403 - No line break is allowed in the LHS of an assignment. Specifically when | |
| 404 unpacking a list |:let-unpack|. This is OK: > | |
| 22171 | 405 [var1, var2] = |
| 21250 | 406 Func() |
| 407 < This does not work: > | |
| 22171 | 408 [var1, |
| 21250 | 409 var2] = |
| 410 Func() | |
| 411 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
| 412 similar commands. This is OK: > | |
| 22171 | 413 echo [1, |
| 21250 | 414 2] [3, |
| 415 4] | |
| 416 < This does not work: > | |
| 22171 | 417 echo [1, 2] |
| 21250 | 418 [3, 4] |
| 419 - No line break is allowed in the arguments of a lambda, between the "{" and | |
| 420 "->". This is OK: > | |
| 22171 | 421 filter(list, {k, v -> |
| 21250 | 422 v > 0}) |
| 423 < This does not work: > | |
| 22171 | 424 filter(list, {k, |
| 21250 | 425 v -> v > 0}) |
|
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426 |
|
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427 |
|
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428 No curly braces expansion ~ |
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429 |
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430 |curly-braces-names| cannot be used. |
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431 |
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432 |
|
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433 No :xit, :t, :append, :change or :insert ~ |
| 19303 | 434 |
|
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435 These commands are too easily confused with local variable names. |
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436 Instead of `:x` or `:xit` you can use `:exit`. |
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437 Instead of `:t` you can use `:copy`. |
|
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438 |
| 19303 | 439 |
| 440 Comparators ~ | |
| 441 | |
| 442 The 'ignorecase' option is not used for comparators that use strings. | |
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443 |
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444 |
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445 White space ~ |
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446 |
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447 Vim9 script enforces proper use of white space. This is no longer allowed: > |
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448 var name=234 # Error! |
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449 var name= 234 # Error! |
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450 var name =234 # Error! |
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451 There must be white space before and after the "=": > |
|
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452 var name = 234 # OK |
| 21250 | 453 White space must also be put before the # that starts a comment after a |
| 454 command: > | |
|
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455 var name = 234# Error! |
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456 var name = 234 # OK |
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457 |
|
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458 White space is required around most operators. |
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459 |
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460 White space is not allowed: |
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461 - Between a function name and the "(": > |
| 22171 | 462 call Func (arg) # Error! |
| 463 call Func | |
| 464 \ (arg) # Error! | |
| 465 call Func(arg) # OK | |
| 466 call Func( | |
| 467 \ arg) # OK | |
| 468 call Func( | |
| 469 \ arg # OK | |
|
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470 \ ) |
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471 |
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472 |
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473 Conditions and expressions ~ |
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474 |
|
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475 Conditions and expressions are mostly working like they do in other languages. |
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476 Some values are different from legacy Vim script: |
|
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477 value legacy Vim script Vim9 script ~ |
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478 0 falsy falsy |
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479 1 truthy truthy |
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480 99 truthy Error! |
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481 "0" falsy Error! |
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482 "99" truthy Error! |
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483 "text" falsy Error! |
|
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484 |
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485 For the "??" operator and when using "!" then there is no error, every value |
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486 is either falsy or truthy. This is mostly like JavaScript, except that an |
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487 empty list and dict is falsy: |
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488 |
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489 type truthy when ~ |
|
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490 bool v:true or 1 |
|
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491 number non-zero |
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492 float non-zero |
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493 string non-empty |
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494 blob non-empty |
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495 list non-empty (different from JavaScript) |
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496 dictionary non-empty (different from JavaScript) |
| 19968 | 497 func when there is a function name |
|
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498 special v:true |
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499 job when not NULL |
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500 channel when not NULL |
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501 class when not NULL |
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502 object when not NULL (TODO: when isTrue() returns v:true) |
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503 |
|
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504 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
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505 one: > |
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506 1 || false == true |
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507 0 || 1 == true |
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508 0 || false == false |
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509 1 && true == true |
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510 0 && 1 == false |
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511 8 || 0 Error! |
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512 'yes' && 0 Error! |
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513 [] || 99 Error! |
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514 |
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515 When using "!" for inverting, there is no error for using any type and the |
|
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516 result is a boolean. "!!" can be used to turn any value into boolean: > |
|
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517 !'yes' == false |
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518 !![] == false |
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519 !![1, 2, 3] == true |
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520 |
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521 When using "`.."` for string concatenation arguments of simple types are |
|
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522 always converted to string: > |
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523 'hello ' .. 123 == 'hello 123' |
| 21825 | 524 'hello ' .. v:true == 'hello v:true' |
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525 |
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526 Simple types are string, float, special and bool. For other types |string()| |
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527 can be used. |
| 22171 | 528 *false* *true* |
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529 In Vim9 script one can use "true" for v:true and "false" for v:false. |
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530 |
| 21825 | 531 Indexing a string with [idx] or [idx, idx] uses character indexes instead of |
| 532 byte indexes. Example: > | |
| 533 echo 'bár'[1] | |
| 534 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
| 535 script this results in the string 'á'. | |
| 536 | |
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537 |
| 21093 | 538 What to watch out for ~ |
| 539 *vim9-gotchas* | |
| 540 Vim9 was designed to be closer to often used programming languages, but at the | |
| 541 same time tries to support the legacy Vim commands. Some compromises had to | |
| 542 be made. Here is a summary of what might be unexpected. | |
| 543 | |
| 544 Ex command ranges need to be prefixed with a colon. > | |
| 22171 | 545 -> # legacy Vim: shifts the previous line to the right |
| 546 ->func() # Vim9: method call in continuation line | |
| 547 :-> # Vim9: shifts the previous line to the right | |
| 21093 | 548 |
| 22171 | 549 %s/a/b # legacy Vim: substitute on all lines |
| 21093 | 550 x = alongname |
| 22171 | 551 % another # Vim9: line continuation without a backslash |
| 552 :%s/a/b # Vim9: substitute on all lines | |
| 553 'text'->func() # Vim9: method call | |
| 554 :'t # legacy Vim: jump to mark m | |
| 21093 | 555 |
| 21676 | 556 Some Ex commands can be confused with assignments in Vim9 script: > |
| 557 g:name = value # assignment | |
| 558 g:pattern:cmd # invalid command - ERROR | |
| 559 :g:pattern:cmd # :global command | |
| 560 | |
| 21093 | 561 Functions defined with `:def` compile the whole function. Legacy functions |
| 562 can bail out, and the following lines are not parsed: > | |
| 563 func Maybe() | |
| 564 if !has('feature') | |
| 565 return | |
| 566 endif | |
| 567 use-feature | |
| 568 endfunc | |
| 569 Vim9 functions are compiled as a whole: > | |
| 570 def Maybe() | |
| 571 if !has('feature') | |
| 572 return | |
| 573 endif | |
| 22171 | 574 use-feature # May give compilation error |
| 21093 | 575 enddef |
| 576 For a workaround, split it in two functions: > | |
| 577 func Maybe() | |
| 578 if has('feature') | |
| 579 call MaybyInner() | |
| 580 endif | |
| 581 endfunc | |
| 582 if has('feature') | |
| 583 def MaybeInner() | |
| 584 use-feature | |
| 585 enddef | |
| 586 endif | |
| 22171 | 587 Or put the unsupported code inside an `if` with a constant expression that |
| 21991 | 588 evaluates to false: > |
| 589 def Maybe() | |
| 590 if has('feature') | |
| 591 use-feature | |
| 592 endif | |
| 593 enddef | |
| 594 Note that for unrecognized commands there is no check for "|" and a following | |
| 595 command. This will give an error for missing `endif`: > | |
| 596 def Maybe() | |
| 597 if has('feature') | use-feature | endif | |
| 598 enddef | |
| 21093 | 599 |
|
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600 ============================================================================== |
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601 |
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602 3. New style functions *fast-functions* |
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603 |
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604 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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605 |
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606 *:def* |
| 21825 | 607 :def[!] {name}([arguments])[: {return-type}] |
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608 Define a new function by the name {name}. The body of |
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609 the function follows in the next lines, until the |
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610 matching `:enddef`. |
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611 |
|
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612 When {return-type} is omitted or is "void" the |
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613 function is not expected to return anything. |
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614 |
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615 {arguments} is a sequence of zero or more argument |
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616 declarations. There are three forms: |
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617 {name}: {type} |
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618 {name} = {value} |
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619 {name}: {type} = {value} |
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620 The first form is a mandatory argument, the caller |
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621 must always provide them. |
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622 The second and third form are optional arguments. |
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623 When the caller omits an argument the {value} is used. |
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624 |
| 20856 | 625 The function will be compiled into instructions when |
| 21499 | 626 called, or when `:disassemble` or `:defcompile` is |
| 627 used. Syntax and type errors will be produced at that | |
| 628 time. | |
| 20856 | 629 |
| 21499 | 630 It is possible to nest `:def` inside another `:def` or |
| 631 `:function` up to about 50 levels deep. | |
| 19303 | 632 |
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633 [!] is used as with `:function`. Note that |
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634 script-local functions cannot be deleted or redefined |
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635 later in Vim9 script. They can only be removed by |
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636 reloading the same script. |
|
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637 |
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638 *:enddef* |
| 21499 | 639 :enddef End of a function defined with `:def`. It should be on |
| 640 a line by its own. | |
|
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641 |
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642 |
|
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643 If the script the function is defined in is Vim9 script, then script-local |
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644 variables can be accessed without the "s:" prefix. They must be defined |
| 20856 | 645 before the function is compiled. If the script the function is defined in is |
| 646 legacy script, then script-local variables must be accessed with the "s:" | |
| 21991 | 647 prefix and they do not need to exist (they can be deleted any time). |
|
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648 |
| 20552 | 649 *:defc* *:defcompile* |
| 650 :defc[ompile] Compile functions defined in the current script that | |
| 651 were not compiled yet. | |
| 652 This will report errors found during the compilation. | |
|
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653 |
| 19404 | 654 *:disa* *:disassemble* |
| 655 :disa[ssemble] {func} Show the instructions generated for {func}. | |
| 656 This is for debugging and testing. | |
|
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657 Note that for command line completion of {func} you |
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658 can prepend "s:" to find script-local functions. |
| 19404 | 659 |
| 21250 | 660 Limitations ~ |
| 661 | |
| 662 Local variables will not be visible to string evaluation. For example: > | |
| 663 def EvalString(): list<string> | |
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664 var list = ['aa', 'bb', 'cc', 'dd'] |
| 21250 | 665 return range(1, 2)->map('list[v:val]') |
| 666 enddef | |
| 667 | |
| 668 The map argument is a string expression, which is evaluated without the | |
| 669 function scope. Instead, use a lambda: > | |
| 670 def EvalString(): list<string> | |
|
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671 var list = ['aa', 'bb', 'cc', 'dd'] |
| 21250 | 672 return range(1, 2)->map({ _, v -> list[v] }) |
| 673 enddef | |
| 674 | |
| 675 | |
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676 ============================================================================== |
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677 |
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678 4. Types *vim9-types* |
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679 |
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680 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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681 |
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682 The following builtin types are supported: |
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683 bool |
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684 number |
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685 float |
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686 string |
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687 blob |
|
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688 list<{type}> |
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689 dict<{type}> |
|
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690 job |
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691 channel |
| 19646 | 692 func |
| 19968 | 693 func: {type} |
|
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694 func({type}, ...) |
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695 func({type}, ...): {type} |
|
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696 |
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697 Not supported yet: |
|
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698 tuple<a: {type}, b: {type}, ...> |
|
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699 |
|
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700 These types can be used in declarations, but no value will have this type: |
| 21499 | 701 {type}|{type} {not implemented yet} |
|
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702 void |
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703 any |
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704 |
|
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|
705 There is no array type, use list<{type}> instead. For a list constant an |
|
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706 efficient implementation is used that avoids allocating lot of small pieces of |
|
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|
707 memory. |
|
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|
708 |
|
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|
709 A partial and function can be declared in more or less specific ways: |
|
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|
710 func any kind of function reference, no type |
| 19968 | 711 checking for arguments or return value |
|
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712 func: {type} any number and type of arguments with specific |
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|
713 return type |
| 19968 | 714 func({type}) function with argument type, does not return |
|
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715 a value |
| 19968 | 716 func({type}): {type} function with argument type and return type |
| 717 func(?{type}) function with type of optional argument, does | |
| 718 not return a value | |
| 719 func(...{type}) function with type of variable number of | |
| 720 arguments, does not return a value | |
| 721 func({type}, ?{type}, ...{type}): {type} | |
| 722 function with: | |
| 723 - type of mandatory argument | |
| 724 - type of optional argument | |
| 725 - type of variable number of arguments | |
| 726 - return type | |
|
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|
727 |
|
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|
728 If the return type is "void" the function does not return a value. |
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|
729 |
|
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|
730 The reference can also be a |Partial|, in which case it stores extra arguments |
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|
731 and/or a dictionary, which are not visible to the caller. Since they are |
|
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|
732 called in the same way the declaration is the same. |
|
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733 |
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|
734 Custom types can be defined with `:type`: > |
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|
735 :type MyList list<string> |
|
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|
736 Custom types must start with a capital letter, to avoid name clashes with |
|
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|
737 builtin types added later, similarly to user functions. |
|
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738 {not implemented yet} |
|
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|
739 |
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|
740 And classes and interfaces can be used as types: > |
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741 :class MyClass |
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742 :var mine: MyClass |
|
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743 |
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|
744 :interface MyInterface |
|
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745 :var mine: MyInterface |
|
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746 |
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747 :class MyTemplate<Targ> |
|
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748 :var mine: MyTemplate<number> |
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749 :var mine: MyTemplate<string> |
|
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|
750 |
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|
751 :class MyInterface<Targ> |
|
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752 :var mine: MyInterface<number> |
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753 :var mine: MyInterface<string> |
|
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754 {not implemented yet} |
|
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|
755 |
|
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|
756 |
|
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|
757 Variable types and type casting ~ |
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|
758 *variable-types* |
|
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|
759 Variables declared in Vim9 script or in a `:def` function have a type, either |
|
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760 specified explicitly or inferred from the initialization. |
|
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|
761 |
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|
762 Global, buffer, window and tab page variables do not have a specific type, the |
|
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|
763 value can be changed at any time, possibly changing the type. Therefore, in |
|
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|
764 compiled code the "any" type is assumed. |
|
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|
765 |
|
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|
766 This can be a problem when the "any" type is undesired and the actual type is |
|
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767 expected to always be the same. For example, when declaring a list: > |
|
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768 var l: list<number> = [1, g:two] |
|
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|
769 This will give an error, because "g:two" has type "any". To avoid this, use a |
|
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770 type cast: > |
|
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771 var l: list<number> = [1, <number>g:two] |
|
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772 < *type-casting* |
|
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773 The compiled code will then check that "g:two" is a number at runtime and give |
|
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774 an error if it isn't. This is called type casting. |
|
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775 |
|
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776 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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777 after the "<" or before the ">" (to avoid them being confused with |
|
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778 smaller-than and bigger-than operators). |
|
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779 |
|
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780 The semantics is that, if needed, a runtime type check is performed. The |
|
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781 value is not actually changed. If you need to change the type, e.g. to change |
|
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782 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
|
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783 string to a number. |
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784 |
|
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785 |
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786 Type inference ~ |
|
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787 *type-inference* |
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788 In general: Whenever the type is clear it can be omitted. For example, when |
|
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789 declaring a variable and giving it a value: > |
|
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790 var name = 0 # infers number type |
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791 var name = 'hello' # infers string type |
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792 |
|
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793 The type of a list and dictionary comes from the common type of the values. |
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794 If the values all have the same type, that type is used for the list or |
|
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795 dictionary. If there is a mix of types, the "any" type is used. > |
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796 [1, 2, 3] list<number> |
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797 ['a', 'b', 'c'] list<string> |
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798 [1, 'x', 3] list<any> |
|
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799 |
| 21991 | 800 |
|
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801 Stricter type checking ~ |
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802 *type-checking* |
| 21991 | 803 In legacy Vim script, where a number was expected, a string would be |
| 804 automatically converted to a number. This was convenient for an actual number | |
| 805 such as "123", but leads to unexpected problems (but no error message) if the | |
| 806 string doesn't start with a number. Quite often this leads to hard-to-find | |
| 807 bugs. | |
| 808 | |
| 809 In Vim9 script this has been made stricter. In most places it works just as | |
| 22171 | 810 before, if the value used matches the expected type. There will sometimes be |
| 811 an error, thus breaking backwards compatibility. For example: | |
| 21991 | 812 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
| 813 - Using a string value when setting a number options. | |
| 814 - Using a number where a string is expected. *E1024* | |
| 815 | |
|
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816 ============================================================================== |
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817 |
|
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818 5. Namespace, Import and Export |
|
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819 *vim9script* *vim9-export* *vim9-import* |
|
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820 |
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821 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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822 |
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823 A Vim9 script can be written to be imported. This means that everything in |
|
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824 the script is local, unless exported. Those exported items, and only those |
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825 items, can then be imported in another script. |
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826 |
| 21991 | 827 You can cheat by using the global namespace explicitly. We will assume here |
| 828 that you don't do that. | |
| 829 | |
|
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830 |
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831 Namespace ~ |
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832 *:vim9script* *:vim9* |
| 19303 | 833 To recognize a file that can be imported the `vim9script` statement must |
|
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834 appear as the first statement in the file. It tells Vim to interpret the |
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835 script in its own namespace, instead of the global namespace. If a file |
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836 starts with: > |
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837 vim9script |
|
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838 var myvar = 'yes' |
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839 Then "myvar" will only exist in this file. While without `vim9script` it would |
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840 be available as `g:myvar` from any other script and function. |
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841 |
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842 The variables at the file level are very much like the script-local "s:" |
| 20115 | 843 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
| 844 deleted. | |
|
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845 |
| 20115 | 846 In Vim9 script the global "g:" namespace can still be used as before. And the |
| 847 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
| 848 declared and they can be deleted. | |
|
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849 |
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850 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
|
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851 Vim default value, like with: > |
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852 :set cpo&vim |
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853 One of the effects is that |line-continuation| is always enabled. |
|
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854 The original value of 'cpoptions' is restored at the end of the script. |
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855 |
|
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|
856 |
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857 Export ~ |
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858 *:export* *:exp* |
| 21499 | 859 Exporting an item can be written as: > |
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860 export const EXPORTED_CONST = 1234 |
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861 export var someValue = ... |
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862 export final someValue = ... |
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863 export const someValue = ... |
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864 export def MyFunc() ... |
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865 export class MyClass ... |
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866 |
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867 As this suggests, only constants, variables, `:def` functions and classes can |
| 21499 | 868 be exported. {classes are not implemented yet} |
|
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869 |
| 20856 | 870 *E1042* |
| 871 `:export` can only be used in Vim9 script, at the script level. | |
|
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872 |
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873 |
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874 Import ~ |
| 20965 | 875 *:import* *:imp* *E1094* |
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876 The exported items can be imported individually in another Vim9 script: > |
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877 import EXPORTED_CONST from "thatscript.vim" |
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878 import MyClass from "myclass.vim" |
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879 |
|
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880 To import multiple items at the same time: > |
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881 import {someValue, MyClass} from "thatscript.vim" |
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882 |
| 19303 | 883 In case the name is ambiguous, another name can be specified: > |
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884 import MyClass as ThatClass from "myclass.vim" |
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885 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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886 |
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887 To import all exported items under a specific identifier: > |
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888 import * as That from 'thatscript.vim' |
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889 |
| 22328 | 890 {not implemented yet: using "This as That"} |
| 891 | |
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892 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
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893 to choose the name "That", but it is highly recommended to use the name of the |
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894 script file to avoid confusion. |
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895 |
| 22171 | 896 `:import` can also be used in legacy Vim script. The imported items still |
| 897 become script-local, even when the "s:" prefix is not given. | |
| 898 | |
|
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899 The script name after `import` can be: |
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900 - A relative path, starting "." or "..". This finds a file relative to the |
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901 location of the script file itself. This is useful to split up a large |
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902 plugin into several files. |
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903 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
| 22723 | 904 will rarely be used. |
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905 - A path not being relative or absolute. This will be found in the |
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906 "import" subdirectories of 'runtimepath' entries. The name will usually be |
|
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907 longer and unique, to avoid loading the wrong file. |
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908 |
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909 Once a vim9 script file has been imported, the result is cached and used the |
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910 next time the same script is imported. It will not be read again. |
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911 *:import-cycle* |
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912 The `import` commands are executed when encountered. If that script (directly |
|
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913 or indirectly) imports the current script, then items defined after the |
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914 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
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915 result in undefined items. |
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916 |
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917 |
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918 Import in an autoload script ~ |
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919 |
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920 For optimal startup speed, loading scripts should be postponed until they are |
| 19303 | 921 actually needed. A recommended mechanism: |
|
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922 |
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923 1. In the plugin define user commands, functions and/or mappings that refer to |
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924 an autoload script. > |
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925 command -nargs=1 SearchForStuff call searchfor#Stuff(<f-args>) |
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926 |
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927 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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928 |
| 21825 | 929 2. In the autoload script do the actual work. You can import items from |
|
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930 other files to split up functionality in appropriate pieces. > |
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931 vim9script |
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932 import FilterFunc from "../import/someother.vim" |
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933 def searchfor#Stuff(arg: string) |
|
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934 var filtered = FilterFunc(arg) |
|
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935 ... |
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936 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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937 must be exactly the same as the prefix for the function name, that is how |
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938 Vim finds the file. |
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939 |
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940 3. Other functionality, possibly shared between plugins, contains the exported |
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941 items and any private items. > |
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942 vim9script |
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943 var localVar = 'local' |
| 22171 | 944 export def FilterFunc(arg: string): string |
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945 ... |
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946 < This goes in .../import/someother.vim. |
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947 |
|
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948 When compiling a `:def` function and a function in an autoload script is |
|
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949 encountered, the script is not loaded until the `:def` function is called. |
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950 |
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951 |
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952 Import in legacy Vim script ~ |
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953 |
| 20856 | 954 If an `import` statement is used in legacy Vim script, the script-local "s:" |
| 955 namespace will be used for the imported item, even when "s:" is not specified. | |
|
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956 |
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957 |
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958 ============================================================================== |
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959 |
| 22328 | 960 6. Future work: classes *vim9-classes* |
| 961 | |
| 962 Above "class" was mentioned a few times, but it has not been implemented yet. | |
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963 Most of Vim9 script can be created without this functionality, and since |
| 22328 | 964 implementing classes is going to be a lot of work, it is left for the future. |
| 965 For now we'll just make sure classes can be added later. | |
| 966 | |
| 967 Thoughts: | |
| 968 - `class` / `endclass`, everything in one file | |
| 969 - Class names are always CamelCase | |
| 970 - Single constructor | |
| 971 - Single inheritance with `class ThisClass extends BaseClass` | |
| 972 - `abstract class` | |
| 973 - `interface` (Abstract class without any implementation) | |
| 974 - `class SomeClass implements SomeInterface` | |
| 975 - Generics for class: `class <Tkey, Tentry>` | |
| 976 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
| 977 | |
| 978 Again, much of this is from TypeScript. | |
| 979 | |
| 980 Some things that look like good additions: | |
| 981 - Use a class as an interface (like Dart) | |
| 982 - Extend a class with methods, using an import (like Dart) | |
| 983 | |
| 984 An important class that will be provided is "Promise". Since Vim is single | |
| 985 threaded, connecting asynchronous operations is a natural way of allowing | |
| 986 plugins to do their work without blocking the user. It's a uniform way to | |
| 987 invoke callbacks and handle timeouts and errors. | |
| 988 | |
| 989 ============================================================================== | |
| 990 | |
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991 9. Rationale *vim9-rationale* |
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992 |
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993 The :def command ~ |
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994 |
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995 Plugin writers have asked for much faster Vim script. Investigations have |
| 19303 | 996 shown that keeping the existing semantics of function calls make this close to |
|
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997 impossible, because of the overhead involved with calling a function, setting |
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998 up the local function scope and executing lines. There are many details that |
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999 need to be handled, such as error messages and exceptions. The need to create |
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1000 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1001 much overhead that cannot be avoided. |
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1002 |
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1003 Therefore the `:def` method to define a new-style function had to be added, |
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1004 which allows for a function with different semantics. Most things still work |
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1005 as before, but some parts do not. A new way to define a function was |
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1006 considered the best way to separate the legacy style code from Vim9 style code. |
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1007 |
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1008 Using "def" to define a function comes from Python. Other languages use |
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1009 "function" which clashes with legacy Vim script. |
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1010 |
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1011 |
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1012 Type checking ~ |
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1013 |
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1014 When compiling lines of Vim commands into instructions as much as possible |
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1015 should be done at compile time. Postponing it to runtime makes the execution |
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1016 slower and means mistakes are found only later. For example, when |
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1017 encountering the "+" character and compiling this into a generic add |
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1018 instruction, at execution time the instruction would have to inspect the type |
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1019 of the arguments and decide what kind of addition to do. And when the |
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1020 type is dictionary throw an error. If the types are known to be numbers then |
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1021 an "add number" instruction can be used, which is faster. The error can be |
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1022 given at compile time, no error handling is needed at runtime, since adding |
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1023 two numbers cannot fail. |
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1024 |
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1025 The syntax for types, using <type> for compound types, is similar to Java. It |
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1026 is easy to understand and widely used. The type names are what were used in |
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1027 Vim before, with some additions such as "void" and "bool". |
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1028 |
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1029 |
| 22328 | 1030 Removing clutter and weirdness ~ |
| 20856 | 1031 |
| 22328 | 1032 Once decided that `:def` functions have different syntax than legacy functions, |
| 1033 we are free to add improvements to make the code more familiar for users who | |
| 1034 know popular programming languages. In other words: remove weird things that | |
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1035 only Vim does. |
| 22328 | 1036 |
| 1037 We can also remove clutter, mainly things that were done to make Vim script | |
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1038 backwards compatible with the good old Vi commands. |
| 20856 | 1039 |
| 22328 | 1040 Examples: |
| 1041 - Drop `:call` for calling a function and `:eval` for manipulating data. | |
| 1042 - Drop using a leading backslash for line continuation, automatically figure | |
| 1043 out where an expression ends. | |
| 20856 | 1044 |
| 22328 | 1045 However, this does require that some things need to change: |
| 1046 - Comments start with # instead of ", to avoid confusing them with strings. | |
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1047 This is good anyway, it is known from several popular languages. |
| 22328 | 1048 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
| 1049 expressions (single quote can be a string or a mark, "/" can be divide or a | |
| 1050 search command, etc.). | |
| 1051 | |
| 1052 Goal is to limit the differences. A good criteria is that when the old syntax | |
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1053 is accidentally used you are very likely to get an error message. |
| 20856 | 1054 |
| 1055 | |
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1056 Syntax and semantics from popular languages ~ |
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1057 |
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1058 Script writers have complained that the Vim script syntax is unexpectedly |
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1059 different from what they are used to. To reduce this complaint popular |
| 20856 | 1060 languages are used as an example. At the same time, we do not want to abandon |
| 1061 the well-known parts of legacy Vim script. | |
|
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1062 |
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1063 For many things TypeScript is followed. It's a recent language that is |
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1064 gaining popularity and has similarities with Vim script. It also has a |
| 22328 | 1065 mix of static typing (a variable always has a known value type) and dynamic |
|
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1066 typing (a variable can have different types, this changes at runtime). Since |
| 22328 | 1067 legacy Vim script is dynamically typed and a lot of existing functionality |
| 1068 (esp. builtin functions) depends on that, while static typing allows for much | |
| 1069 faster execution, we need to have this mix in Vim9 script. | |
| 1070 | |
| 22171 | 1071 There is no intention to completely match TypeScript syntax and semantics. We |
| 1072 just want to take those parts that we can use for Vim and we expect Vim users | |
| 22328 | 1073 will be happy with. TypeScript is a complex language with its own history, |
| 1074 advantages and disadvantages. To get an idea of the disadvantages read the | |
| 1075 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
|
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1076 parts" and read the "Things to avoid" section. |
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1077 |
| 22328 | 1078 People familiar with other languages (Java, Python, etc.) will also find |
| 1079 things in TypeScript that they do not like or do not understand. We'll try to | |
| 1080 avoid those things. | |
|
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1081 |
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1082 Specific items from TypeScript we avoid: |
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1083 - Overloading "+", using it both for addition and string concatenation. This |
|
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1084 goes against legacy Vim script and often leads to mistakes. For that reason |
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1085 we will keep using ".." for string concatenation. Lua also uses ".." this |
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1086 way. And it allows for conversion to string for more values. |
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1087 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
|
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1088 cannot assign the value to a boolean. That is inconsistent and can be |
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1089 annoying. Vim recognizes an expression with && or || and allows using the |
|
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1090 result as a bool. TODO: to be reconsidered |
|
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1091 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
|
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1092 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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1093 Falsy. |
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1094 - TypeScript has various "Readonly" types, which have limited usefulness, |
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1095 since a type cast can remove the immutable nature. Vim locks the value, |
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1096 which is more flexible, but is only checked at runtime. |
| 22171 | 1097 |
|
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1098 |
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1099 Declarations ~ |
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1100 |
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1101 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
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1102 are used. That is different, thus it's good to use a different command: |
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1103 `:var`. This is used in many languages. The semantics might be slightly |
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1104 different, but it's easily recognized as a declaration. |
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1105 |
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1106 Using `:const` for constants is common, but the semantics vary. Some |
|
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1107 languages only make the variable immutable, others also make the value |
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1108 immutable. Since "final" is well known from Java for only making the variable |
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1109 immutable we decided to use that. And then `:const` can be used for making |
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1110 both immutable. This was also used in legacy Vim script and the meaning is |
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1111 almost the same. |
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1112 |
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1113 What we end up with is very similar to Dart: > |
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1114 :var name # mutable variable and value |
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1115 :final name # immutable variable, mutable value |
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1116 :const name # immutable variable and value |
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1117 |
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1118 Since legacy and Vim9 script will be mixed and global variables will be |
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1119 shared, optional type checking is desirable. Also, type inference will avoid |
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1120 the need for specifying the type in many cases. The TypeScript syntax fits |
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1121 best for adding types to declarations: > |
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1122 var name: string # string type is specified |
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1123 ... |
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1124 name = 'John' |
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1125 const greeting = 'hello' # string type is inferred |
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1126 |
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1127 This is how we put types in a declaration: > |
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1128 var mylist: list<string> |
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1129 final mylist: list<string> = ['foo'] |
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1130 def Func(arg1: number, arg2: string): bool |
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1131 |
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1132 Two alternatives were considered: |
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1133 1. Put the type before the name, like Dart: > |
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1134 var list<string> mylist |
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1135 final list<string> mylist = ['foo'] |
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1136 def Func(number arg1, string arg2) bool |
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1137 2. Put the type after the variable name, but do not use a colon, like Go: > |
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1138 var mylist list<string> |
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1139 final mylist list<string> = ['foo'] |
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1140 def Func(arg1 number, arg2 string) bool |
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1141 |
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1142 The first is more familiar for anyone used to C or Java. The second one |
| 22565 | 1143 doesn't really have an advantage over the first, so let's discard the second. |
|
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1144 |
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1145 Since we use type inference the type can be left out when it can be inferred |
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1146 from the value. This means that after `var` we don't know if a type or a name |
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1147 follows. That makes parsing harder, not only for Vim but also for humans. |
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1148 Also, it will not be allowed to use a variable name that could be a type name, |
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1149 using `var string string` is too confusing. |
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1150 |
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1151 The chosen syntax, using a colon to separate the name from the type, adds |
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1152 punctuation, but it actually makes it easier to recognize the parts of a |
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1153 declaration. |
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1154 |
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1155 |
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1156 Expressions ~ |
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1157 |
| 22565 | 1158 Expression evaluation was already close to what other languages are doing. |
| 1159 Some details are unexpected and can be improved. For example a boolean | |
| 1160 condition would accept a string, convert it to a number and check if the | |
| 1161 number is non-zero. This is unexpected and often leads to mistakes, since | |
| 1162 text not starting with a number would be converted to zero, which is | |
| 22723 | 1163 considered false. Thus using a string for a condition would often not give an |
| 1164 error and be considered false. That is confusing. | |
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1165 |
| 22565 | 1166 In Vim9 type checking is more strict to avoid mistakes. Where a condition is |
| 1167 used, e.g. with the `:if` command and the `||` operator, only boolean-like | |
| 1168 values are accepted: | |
| 1169 true: `true`, `v:true`, `1`, `0 < 9` | |
| 1170 false: `false`, `v:false`, `0`, `0 > 9` | |
| 1171 Note that the number zero is false and the number one is true. This is more | |
| 22723 | 1172 permissive than most other languages. It was done because many builtin |
| 22565 | 1173 functions return these values. |
|
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1174 |
| 22565 | 1175 If you have any type of value and want to use it as a boolean, use the `!!` |
| 1176 operator: | |
| 1177 true: !`!'text'`, `!![99]`, `!!{'x': 1}`, `!!99` | |
| 1178 false: `!!''`, `!![]`, `!!{}` | |
| 1179 | |
| 1180 From a language like JavaScript we have this handy construct: > | |
| 1181 GetName() || 'unknown' | |
| 1182 However, this conflicts with only allowing a boolean for a condition. | |
| 1183 Therefore the "??" operator was added: > | |
| 1184 GetName() ?? 'unknown' | |
| 1185 Here you can explicitly express your intention to use the value as-is and not | |
| 1186 result in a boolean. This is called the |falsy-operator|. | |
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1187 |
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1188 |
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1189 Import and Export ~ |
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1190 |
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1191 A problem of legacy Vim script is that by default all functions and variables |
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1192 are global. It is possible to make them script-local, but then they are not |
| 22171 | 1193 available in other scripts. This defies the concept of a package that only |
| 1194 exports selected items and keeps the rest local. | |
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1195 |
| 21825 | 1196 In Vim9 script a mechanism very similar to the JavaScript import and export |
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1197 mechanism is supported. It is a variant to the existing `:source` command |
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1198 that works like one would expect: |
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1199 - Instead of making everything global by default, everything is script-local, |
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1200 unless exported. |
| 22171 | 1201 - When importing a script the symbols that are imported are explicitly listed, |
| 1202 avoiding name conflicts and failures if functionality is added later. | |
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1203 - The mechanism allows for writing a big, long script with a very clear API: |
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1204 the exported function(s) and class(es). |
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1205 - By using relative paths loading can be much faster for an import inside of a |
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1206 package, no need to search many directories. |
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1207 - Once an import has been used, it can be cached and loading it again can be |
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1208 avoided. |
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1209 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1210 |
| 20856 | 1211 When sourcing a Vim9 script from a legacy script, only the items defined |
| 1212 globally can be used, not the exported items. Alternatives considered: | |
| 1213 - All the exported items become available as script-local items. This makes | |
| 22171 | 1214 it uncontrollable what items get defined and likely soon leads to trouble. |
| 20856 | 1215 - Use the exported items and make them global. Disadvantage is that it's then |
| 1216 not possible to avoid name clashes in the global namespace. | |
| 1217 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
| 1218 makes it difficult to use scripts for testing, or sourcing them from the | |
| 1219 command line to try them out. | |
| 22171 | 1220 Note that you can also use `:import` in legacy Vim script, see above. |
| 20856 | 1221 |
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1222 |
| 22328 | 1223 Compiling functions early ~ |
| 1224 | |
| 1225 Functions are compiled when called or when `:defcompile` is used. Why not | |
| 1226 compile them early, so that syntax and type errors are reported early? | |
| 1227 | |
| 1228 The functions can't be compiled right away when encountered, because there may | |
| 1229 be forward references to functions defined later. Consider defining functions | |
| 1230 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
| 1231 to reorder the functions to avoid forward references. | |
| 1232 | |
| 1233 An alternative would be to first scan through the file to locate items and | |
| 1234 figure out their type, so that forward references are found, and only then | |
| 1235 execute the script and compile the functions. This means the script has to be | |
| 1236 parsed twice, which is slower, and some conditions at the script level, such | |
| 1237 as checking if a feature is supported, are hard to use. An attempt was made | |
| 1238 to see if it works, but it turned out to be impossible to make work nicely. | |
| 1239 | |
| 1240 It would be possible to compile all the functions at the end of the script. | |
| 1241 The drawback is that if a function never gets called, the overhead of | |
| 1242 compiling it counts anyway. Since startup speed is very important, in most | |
| 1243 cases it's better to do it later and accept that syntax and type errors are | |
| 1244 only reported then. In case these errors should be found early, e.g. when | |
| 1245 testing, the `:defcompile` command will help out. | |
| 1246 | |
| 1247 | |
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1248 Why not use an embedded language? ~ |
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1249 |
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1250 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
| 22328 | 1251 these interfaces have never become widely used, for various reasons. When |
| 1252 Vim9 was designed a decision was made to make these interfaces lower priority | |
| 1253 and concentrate on Vim script. | |
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1254 |
| 22328 | 1255 Still, plugin writers may find other languages more familiar, want to use |
| 1256 existing libraries or see a performance benefit. We encourage plugin authors | |
| 1257 to write code in any language and run it as an external tool, using jobs and | |
| 1258 channels. We can try to make this easier somehow. | |
| 1259 | |
| 1260 Using an external tool also has disadvantages. An alternative is to convert | |
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1261 the tool into Vim script. For that to be possible without too much |
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1262 translation, and keeping the code fast at the same time, the constructs of the |
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1263 tool need to be supported. Since most languages support classes the lack of |
| 22171 | 1264 support for classes in Vim is then a problem. |
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1265 |
| 22328 | 1266 |
| 1267 Classes ~ | |
| 1268 | |
| 1269 Vim supports a kind-of object oriented programming by adding methods to a | |
| 1270 dictionary. With some care this can be made to work, but it does not look | |
| 1271 like real classes. On top of that, it's quite slow, because of the use of | |
| 1272 dictionaries. | |
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1273 |
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1274 The support of classes in Vim9 script is a "minimal common functionality" of |
| 22171 | 1275 class support in most languages. It works much like Java, which is the most |
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1276 popular programming language. |
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1277 |
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1278 |
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1279 |
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1280 vim:tw=78:ts=8:noet:ft=help:norl: |