Mercurial > vim
annotate runtime/doc/vim9.txt @ 22272:eb1f5f618c75 v8.2.1685
patch 8.2.1685: Vim9: cannot declare a constant value
Commit: https://github.com/vim/vim/commit/0b4c66c67a083f25816b9cdb8e76a41e02d9f560
Author: Bram Moolenaar <Bram@vim.org>
Date: Mon Sep 14 21:39:44 2020 +0200
patch 8.2.1685: Vim9: cannot declare a constant value
Problem: Vim9: cannot declare a constant value.
Solution: Introduce ":const!".
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Mon, 14 Sep 2020 21:45:04 +0200 |
| parents | d4c7b3e9cd17 |
| children | 75ff30a78189 |
| rev | line source |
|---|---|
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1 *vim9.txt* For Vim version 8.2. Last change: 2020 Sep 13 |
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3 |
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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| |
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22 |
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23 9. Rationale |vim9-rationale| |
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24 |
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25 ============================================================================== |
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26 |
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27 1. What is Vim9 script? *vim9-script* |
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28 |
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29 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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30 |
| 20241 | 31 Vim script has been growing over time, while preserving backwards |
| 32 compatibility. That means bad choices from the past often can't be changed | |
| 20965 | 33 and compatibility with Vi restricts possible solutions. Execution is quite |
| 20241 | 34 slow, each line is parsed every time it is executed. |
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35 |
| 20241 | 36 The main goal of Vim9 script is to drastically improve performance. This is |
| 37 accomplished by compiling commands into instructions that can be efficiently | |
| 38 executed. An increase in execution speed of 10 to 100 times can be expected. | |
| 39 | |
| 40 A secondary goal is to avoid Vim-specific constructs and get closer to | |
| 41 commonly used programming languages, such as JavaScript, TypeScript and Java. | |
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42 |
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43 The performance improvements can only be achieved by not being 100% backwards |
| 20552 | 44 compatible. For example, making function arguments available in the |
| 45 "a:" dictionary adds quite a lot of overhead. In a Vim9 function this | |
| 46 dictionary is not available. Other differences are more subtle, such as how | |
| 47 errors are handled. | |
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48 |
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49 The Vim9 script syntax and semantics are used in: |
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50 - a function defined with the `:def` command |
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51 - a script file where the first command is `vim9script` |
| 21991 | 52 - an autocommand defined in the context of these |
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53 |
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54 When using `:function` in a Vim9 script file the legacy syntax is used. |
| 20241 | 55 However, this can be confusing and is therefore discouraged. |
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56 |
| 20241 | 57 Vim9 script and legacy Vim script can be mixed. There is no requirement to |
| 58 rewrite old scripts, they keep working as before. | |
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59 |
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60 ============================================================================== |
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61 |
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62 2. Differences from legacy Vim script *vim9-differences* |
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63 |
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64 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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65 |
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66 Comments starting with # ~ |
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67 |
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68 In legacy Vim script comments start with double quote. In Vim9 script |
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69 comments start with #. > |
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70 # declarations |
| 20965 | 71 let count = 0 # number of occurrences |
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72 |
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73 The reason is that a double quote can also be the start of a string. In many |
| 21825 | 74 places, especially halfway through an expression with a line break, it's hard |
| 75 to tell what the meaning is, since both a string and a comment can be followed | |
| 76 by arbitrary text. To avoid confusion only # comments are recognized. This | |
| 77 is the same as in shell scripts and Python programs. | |
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78 |
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79 In Vi # is a command to list text with numbers. In Vim9 script you can use |
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80 `:number` for that. > |
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81 101 number |
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82 |
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83 To improve readability there must be a space between a command and the # |
| 20115 | 84 that starts a comment. Note that #{ is the start of a dictionary, therefore |
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85 it does not start a comment. |
| 20115 | 86 |
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87 |
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88 Vim9 functions ~ |
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89 |
| 20241 | 90 A function defined with `:def` is compiled. Execution is many times faster, |
| 91 often 10x to 100x times. | |
| 92 | |
| 20552 | 93 Many errors are already found when compiling, before the function is executed. |
| 20241 | 94 The syntax is strict, to enforce code that is easy to read and understand. |
| 95 | |
| 21991 | 96 Compilation is done when: |
| 97 - the function is first called | |
| 98 - when the `:defcompile` command is encountered in the script where the | |
| 99 function was defined | |
| 100 - `:disassemble` is used for the function. | |
| 101 - a function that is compiled calls the function or uses it as a function | |
| 102 reference | |
| 20552 | 103 |
| 104 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
| 105 "closure". A `:def` function always aborts on an error, does not get a range | |
| 106 passed and cannot be a "dict" function. | |
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107 |
| 20241 | 108 The argument types and return type need to be specified. The "any" type can |
| 109 be used, type checking will then be done at runtime, like with legacy | |
| 110 functions. | |
| 111 | |
| 21825 | 112 Arguments are accessed by name, without "a:", just like any other language. |
| 113 There is no "a:" dictionary or "a:000" list. | |
| 20241 | 114 |
| 115 Variable arguments are defined as the last argument, with a name and have a | |
| 21825 | 116 list type, similar to TypeScript. For example, a list of numbers: > |
| 22171 | 117 def MyFunc(...itemlist: list<number>) |
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118 for item in itemlist |
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119 ... |
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120 |
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121 |
| 20241 | 122 Functions and variables are script-local by default ~ |
| 20856 | 123 *vim9-scopes* |
| 20115 | 124 When using `:function` or `:def` to specify a new function at the script level |
| 125 in a Vim9 script, the function is local to the script, as if "s:" was | |
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126 prefixed. Using the "s:" prefix is optional. To define or use a global |
| 21676 | 127 function or variable the "g:" prefix should be used. For functions in an |
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128 autoload script the "name#" prefix is sufficient. > |
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129 def ThisFunction() # script-local |
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130 def s:ThisFunction() # script-local |
| 22171 | 131 def g:ThatFunction() # global |
| 132 def ThatFunction() # global if no local ThatFunction() | |
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133 def scriptname#function() # autoload |
| 20115 | 134 |
| 135 When using `:function` or `:def` to specify a new function inside a function, | |
| 136 the function is local to the function. It is not possible to define a | |
| 20241 | 137 script-local function inside a function. It is possible to define a global |
| 138 function, using the "g:" prefix. | |
| 20115 | 139 |
| 140 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
| 21676 | 141 prefer using a local function (in the function scope, script scope or |
| 142 imported) before looking for a global function. | |
| 20552 | 143 In all cases the function must be defined before used. That is when it is |
| 144 first called or when `:defcompile` causes the call to be compiled. | |
| 20241 | 145 |
| 21676 | 146 The result is that functions and variables without a namespace can usually be |
| 20241 | 147 found in the script, either defined there or imported. Global functions and |
| 21676 | 148 variables could be defined anywhere (good luck finding out where!). |
| 20115 | 149 |
| 21825 | 150 Global functions can still be defined and deleted at nearly any time. In |
| 20317 | 151 Vim9 script script-local functions are defined once when the script is sourced |
| 20552 | 152 and cannot be deleted or replaced. |
| 20115 | 153 |
| 154 | |
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155 Variable declarations with :let and :const ~ |
| 20856 | 156 *vim9-declaration* |
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157 Local variables need to be declared with `:let`. Local constants need to be |
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158 declared with `:const`. We refer to both as "variables". |
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159 |
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160 Variables can be local to a script, function or code block: > |
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161 vim9script |
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162 let script_var = 123 |
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163 def SomeFunc() |
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164 let func_var = script_var |
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165 if cond |
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166 let block_var = func_var |
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167 ... |
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168 |
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169 The variables are only visible in the block where they are defined and nested |
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170 blocks. Once the block ends the variable is no longer accessible: > |
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171 if cond |
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172 let inner = 5 |
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173 else |
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174 let inner = 0 |
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175 endif |
| 22171 | 176 echo inner # Error! |
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177 |
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178 The declaration must be done earlier: > |
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179 let inner: number |
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180 if cond |
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181 inner = 5 |
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182 else |
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183 inner = 0 |
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184 endif |
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185 echo inner |
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186 |
| 20552 | 187 To intentionally avoid a variable being available later, a block can be used: |
| 188 > | |
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189 { |
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190 let temp = 'temp' |
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191 ... |
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192 } |
| 22171 | 193 echo temp # Error! |
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194 |
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195 Declaring a variable with a type but without an initializer will initialize to |
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196 zero, false or empty. |
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197 |
| 19303 | 198 An existing variable cannot be assigned to with `:let`, since that implies a |
| 21499 | 199 declaration. Global, window, tab, buffer and Vim variables can only be used |
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200 without `:let`, because they are not really declared, they can also be deleted |
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201 with `:unlet`. |
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202 |
| 21676 | 203 Variables and functions cannot shadow previously defined or imported variables |
| 204 and functions. | |
|
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205 Variables may shadow Ex commands, rename the variable if needed. |
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206 |
| 20241 | 207 Global variables and user defined functions must be prefixed with "g:", also |
| 208 at the script level. > | |
| 19968 | 209 vim9script |
| 210 let script_local = 'text' | |
| 21499 | 211 g:global = 'value' |
| 20241 | 212 let Funcref = g:ThatFunction |
| 19968 | 213 |
|
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214 Since "&opt = value" is now assigning a value to option "opt", ":&" cannot be |
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215 used to repeat a `:substitute` command. |
|
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216 *vim9-const* |
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217 In legacy Vim script "const list = []" would make the variable "list" |
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218 immutable and also the value. Thus you cannot add items to the list. This |
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219 differs from what many languages do. Vim9 script does it like TypeScript: only |
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220 "list" is immutable, the value can be changed. |
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221 |
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222 One can use `:const!` to make both the variable and the value immutable. Use |
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223 this for composite structures that you want to make sure will not be modified. |
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224 |
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225 How this works: > |
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226 vim9script |
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227 const list = [1, 2] |
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228 list = [3, 4] # Error! |
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229 list[0] = 2 # OK |
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230 |
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231 const! LIST = [1, 2] |
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232 LIST = [3, 4] # Error! |
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233 LIST[0] = 2 # Error! |
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234 It is common to write constants as ALL_CAPS, but you don't have to. |
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235 |
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236 The constant only applies to the value itself, not what it refers to. > |
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237 cont females = ["Mary"] |
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238 const! NAMES = [["John", "Peter"], females] |
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239 NAMES[0] = ["Jack"] # Error! |
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240 NAMES[0][0] = ["Jack"] # Error! |
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241 NAMES[1] = ["Emma"] # Error! |
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242 Names[1][0] = "Emma" # OK, now females[0] == "Emma" |
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243 |
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244 Rationale: TypeScript has no way to make the value immutable. One can use |
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245 immutable types, but that quickly gets complicated for nested values. And |
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246 with a type cast the value can be made mutable again, which means there is no |
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247 guarantee the value won't change. Vim supports immutable values, in legacy |
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248 script this was done with `:lockvar`. But that is an extra statement and also |
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249 applies to nested values. Therefore the solution to use `:const!`. |
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250 |
| 21499 | 251 *E1092* |
| 252 Declaring more than one variable at a time, using the unpack notation, is | |
| 253 currently not supported: > | |
| 254 let [v1, v2] = GetValues() # Error! | |
| 255 That is because the type needs to be inferred from the list item type, which | |
| 256 isn't that easy. | |
| 257 | |
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258 |
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259 Omitting :call and :eval ~ |
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260 |
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261 Functions can be called without `:call`: > |
| 22171 | 262 writefile(lines, 'file') |
| 19303 | 263 Using `:call` is still possible, but this is discouraged. |
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264 |
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265 A method call without `eval` is possible, so long as the start is an |
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266 identifier or can't be an Ex command. Examples: > |
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267 myList->add(123) |
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268 g:myList->add(123) |
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269 [1, 2, 3]->Process() |
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270 #{a: 1, b: 2}->Process() |
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271 {'a': 1, 'b': 2}->Process() |
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272 "foobar"->Process() |
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273 ("foobar")->Process() |
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274 'foobar'->Process() |
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275 ('foobar')->Process() |
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276 |
| 21825 | 277 In the rare case there is ambiguity between a function name and an Ex command, |
| 21676 | 278 prepend ":" to make clear you want to use the Ex command. For example, there |
| 279 is both the `:substitute` command and the `substitute()` function. When the | |
| 280 line starts with `substitute(` this will use the function. Prepend a colon to | |
| 281 use the command instead: > | |
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282 :substitute(pattern (replacement ( |
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283 |
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284 Note that while variables need to be defined before they can be used, |
| 21825 | 285 functions can be called before being defined. This is required to allow |
| 286 for cyclic dependencies between functions. It is slightly less efficient, | |
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287 since the function has to be looked up by name. And a typo in the function |
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288 name will only be found when the function is called. |
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289 |
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290 |
| 19968 | 291 Omitting function() ~ |
| 292 | |
| 293 A user defined function can be used as a function reference in an expression | |
| 294 without `function()`. The argument types and return type will then be checked. | |
| 295 The function must already have been defined. > | |
| 296 | |
| 297 let Funcref = MyFunction | |
| 298 | |
| 299 When using `function()` the resulting type is "func", a function with any | |
| 300 number of arguments and any return type. The function can be defined later. | |
| 301 | |
| 302 | |
|
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303 Automatic line continuation ~ |
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304 |
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305 In many cases it is obvious that an expression continues on the next line. In |
| 21676 | 306 those cases there is no need to prefix the line with a backslash |
| 307 |line-continuation|. For example, when a list spans multiple lines: > | |
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308 let mylist = [ |
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309 'one', |
|
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310 'two', |
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311 ] |
|
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312 And when a dict spans multiple lines: > |
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313 let mydict = #{ |
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314 one: 1, |
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315 two: 2, |
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316 } |
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317 Function call: > |
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318 let result = Func( |
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319 arg1, |
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320 arg2 |
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321 ) |
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322 |
|
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323 For binary operators in expressions not in [], {} or () a line break is |
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324 possible just before or after the operator. For example: > |
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325 let text = lead |
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326 .. middle |
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327 .. end |
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328 let total = start + |
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329 end - |
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330 correction |
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331 let result = positive |
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332 ? PosFunc(arg) |
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333 : NegFunc(arg) |
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334 |
| 21499 | 335 For a method call using "->" and a member using a dot, a line break is allowed |
| 336 before it: > | |
| 20965 | 337 let result = GetBuilder() |
| 338 ->BuilderSetWidth(333) | |
| 339 ->BuilderSetHeight(777) | |
| 340 ->BuilderBuild() | |
| 21499 | 341 let result = MyDict |
| 342 .member | |
| 20965 | 343 |
|
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344 < *E1050* |
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345 To make it possible for the operator at the start of the line to be |
| 21250 | 346 recognized, it is required to put a colon before a range. This will add |
|
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347 "start" and print: > |
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348 let result = start |
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349 + print |
| 21250 | 350 Like this: > |
| 351 let result = start + print | |
| 352 | |
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353 This will assign "start" and print a line: > |
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354 let result = start |
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355 :+ print |
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356 |
|
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357 It is also possible to split a function header over multiple lines, in between |
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358 arguments: > |
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359 def MyFunc( |
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360 text: string, |
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361 separator = '-' |
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362 ): string |
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363 |
| 21250 | 364 Notes: |
| 365 - "enddef" cannot be used at the start of a continuation line, it ends the | |
| 366 current function. | |
| 367 - No line break is allowed in the LHS of an assignment. Specifically when | |
| 368 unpacking a list |:let-unpack|. This is OK: > | |
| 22171 | 369 [var1, var2] = |
| 21250 | 370 Func() |
| 371 < This does not work: > | |
| 22171 | 372 [var1, |
| 21250 | 373 var2] = |
| 374 Func() | |
| 375 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
| 376 similar commands. This is OK: > | |
| 22171 | 377 echo [1, |
| 21250 | 378 2] [3, |
| 379 4] | |
| 380 < This does not work: > | |
| 22171 | 381 echo [1, 2] |
| 21250 | 382 [3, 4] |
| 383 - No line break is allowed in the arguments of a lambda, between the "{" and | |
| 384 "->". This is OK: > | |
| 22171 | 385 filter(list, {k, v -> |
| 21250 | 386 v > 0}) |
| 387 < This does not work: > | |
| 22171 | 388 filter(list, {k, |
| 21250 | 389 v -> v > 0}) |
|
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390 |
|
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391 |
|
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392 No curly braces expansion ~ |
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393 |
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394 |curly-braces-names| cannot be used. |
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395 |
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396 |
|
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397 No :xit, :t, :append, :change or :insert ~ |
| 19303 | 398 |
|
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399 These commands are too easily confused with local variable names. |
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400 Instead of `:x` or `:xit` you can use `:exit`. |
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401 Instead of `:t` you can use `:copy`. |
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402 |
| 19303 | 403 |
| 404 Comparators ~ | |
| 405 | |
| 406 The 'ignorecase' option is not used for comparators that use strings. | |
|
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407 |
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408 |
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409 White space ~ |
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410 |
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411 Vim9 script enforces proper use of white space. This is no longer allowed: > |
| 22171 | 412 let var=234 # Error! |
| 413 let var= 234 # Error! | |
| 414 let var =234 # Error! | |
|
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415 There must be white space before and after the "=": > |
| 22171 | 416 let var = 234 # OK |
| 21250 | 417 White space must also be put before the # that starts a comment after a |
| 418 command: > | |
|
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419 let var = 234# Error! |
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420 let var = 234 # OK |
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421 |
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422 White space is required around most operators. |
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423 |
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424 White space is not allowed: |
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425 - Between a function name and the "(": > |
| 22171 | 426 call Func (arg) # Error! |
| 427 call Func | |
| 428 \ (arg) # Error! | |
| 429 call Func(arg) # OK | |
| 430 call Func( | |
| 431 \ arg) # OK | |
| 432 call Func( | |
| 433 \ arg # OK | |
|
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434 \ ) |
|
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435 |
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436 |
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437 Conditions and expressions ~ |
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438 |
| 21825 | 439 Conditions and expressions are mostly working like they do in JavaScript. A |
|
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440 difference is made where JavaScript does not work like most people expect. |
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441 Specifically, an empty list is falsey. |
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442 |
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443 Any type of variable can be used as a condition, there is no error, not even |
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444 for using a list or job. This is very much like JavaScript, but there are a |
|
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445 few exceptions. |
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446 |
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447 type TRUE when ~ |
|
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448 bool v:true or 1 |
|
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449 number non-zero |
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450 float non-zero |
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451 string non-empty |
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452 blob non-empty |
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453 list non-empty (different from JavaScript) |
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454 dictionary non-empty (different from JavaScript) |
| 19968 | 455 func when there is a function name |
|
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456 special v:true |
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457 job when not NULL |
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458 channel when not NULL |
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459 class when not NULL |
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460 object when not NULL (TODO: when isTrue() returns v:true) |
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461 |
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462 The boolean operators "||" and "&&" do not change the value: > |
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463 8 || 2 == 8 |
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464 0 || 2 == 2 |
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465 0 || '' == '' |
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466 8 && 2 == 2 |
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467 0 && 2 == 0 |
|
21353
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468 2 && 0 == 0 |
|
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469 [] && 2 == [] |
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470 |
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471 When using `..` for string concatenation arguments of simple types are always |
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472 converted to string. > |
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473 'hello ' .. 123 == 'hello 123' |
| 21825 | 474 'hello ' .. v:true == 'hello v:true' |
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475 |
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476 Simple types are string, float, special and bool. For other types |string()| |
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477 can be used. |
| 22171 | 478 *false* *true* |
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479 In Vim9 script one can use "true" for v:true and "false" for v:false. |
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480 |
| 21825 | 481 Indexing a string with [idx] or [idx, idx] uses character indexes instead of |
| 482 byte indexes. Example: > | |
| 483 echo 'bár'[1] | |
| 484 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
| 485 script this results in the string 'á'. | |
| 486 | |
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487 |
| 21093 | 488 What to watch out for ~ |
| 489 *vim9-gotchas* | |
| 490 Vim9 was designed to be closer to often used programming languages, but at the | |
| 491 same time tries to support the legacy Vim commands. Some compromises had to | |
| 492 be made. Here is a summary of what might be unexpected. | |
| 493 | |
| 494 Ex command ranges need to be prefixed with a colon. > | |
| 22171 | 495 -> # legacy Vim: shifts the previous line to the right |
| 496 ->func() # Vim9: method call in continuation line | |
| 497 :-> # Vim9: shifts the previous line to the right | |
| 21093 | 498 |
| 22171 | 499 %s/a/b # legacy Vim: substitute on all lines |
| 21093 | 500 x = alongname |
| 22171 | 501 % another # Vim9: line continuation without a backslash |
| 502 :%s/a/b # Vim9: substitute on all lines | |
| 503 'text'->func() # Vim9: method call | |
| 504 :'t # legacy Vim: jump to mark m | |
| 21093 | 505 |
| 21676 | 506 Some Ex commands can be confused with assignments in Vim9 script: > |
| 507 g:name = value # assignment | |
| 508 g:pattern:cmd # invalid command - ERROR | |
| 509 :g:pattern:cmd # :global command | |
| 510 | |
| 21093 | 511 Functions defined with `:def` compile the whole function. Legacy functions |
| 512 can bail out, and the following lines are not parsed: > | |
| 513 func Maybe() | |
| 514 if !has('feature') | |
| 515 return | |
| 516 endif | |
| 517 use-feature | |
| 518 endfunc | |
| 519 Vim9 functions are compiled as a whole: > | |
| 520 def Maybe() | |
| 521 if !has('feature') | |
| 522 return | |
| 523 endif | |
| 22171 | 524 use-feature # May give compilation error |
| 21093 | 525 enddef |
| 526 For a workaround, split it in two functions: > | |
| 527 func Maybe() | |
| 528 if has('feature') | |
| 529 call MaybyInner() | |
| 530 endif | |
| 531 endfunc | |
| 532 if has('feature') | |
| 533 def MaybeInner() | |
| 534 use-feature | |
| 535 enddef | |
| 536 endif | |
| 22171 | 537 Or put the unsupported code inside an `if` with a constant expression that |
| 21991 | 538 evaluates to false: > |
| 539 def Maybe() | |
| 540 if has('feature') | |
| 541 use-feature | |
| 542 endif | |
| 543 enddef | |
| 544 Note that for unrecognized commands there is no check for "|" and a following | |
| 545 command. This will give an error for missing `endif`: > | |
| 546 def Maybe() | |
| 547 if has('feature') | use-feature | endif | |
| 548 enddef | |
| 21093 | 549 |
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550 ============================================================================== |
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551 |
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552 3. New style functions *fast-functions* |
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553 |
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554 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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555 |
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556 *:def* |
| 21825 | 557 :def[!] {name}([arguments])[: {return-type}] |
|
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558 Define a new function by the name {name}. The body of |
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559 the function follows in the next lines, until the |
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560 matching `:enddef`. |
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561 |
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562 When {return-type} is omitted or is "void" the |
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563 function is not expected to return anything. |
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564 |
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565 {arguments} is a sequence of zero or more argument |
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566 declarations. There are three forms: |
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567 {name}: {type} |
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568 {name} = {value} |
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569 {name}: {type} = {value} |
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570 The first form is a mandatory argument, the caller |
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571 must always provide them. |
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572 The second and third form are optional arguments. |
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573 When the caller omits an argument the {value} is used. |
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574 |
| 20856 | 575 The function will be compiled into instructions when |
| 21499 | 576 called, or when `:disassemble` or `:defcompile` is |
| 577 used. Syntax and type errors will be produced at that | |
| 578 time. | |
| 20856 | 579 |
| 21499 | 580 It is possible to nest `:def` inside another `:def` or |
| 581 `:function` up to about 50 levels deep. | |
| 19303 | 582 |
| 20552 | 583 [!] is used as with `:function`. Note that in Vim9 |
| 584 script script-local functions cannot be deleted or | |
| 20856 | 585 redefined later in the same script. |
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586 |
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587 *:enddef* |
| 21499 | 588 :enddef End of a function defined with `:def`. It should be on |
| 589 a line by its own. | |
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590 |
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591 |
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592 If the script the function is defined in is Vim9 script, then script-local |
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593 variables can be accessed without the "s:" prefix. They must be defined |
| 20856 | 594 before the function is compiled. If the script the function is defined in is |
| 595 legacy script, then script-local variables must be accessed with the "s:" | |
| 21991 | 596 prefix and they do not need to exist (they can be deleted any time). |
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597 |
| 20552 | 598 *:defc* *:defcompile* |
| 599 :defc[ompile] Compile functions defined in the current script that | |
| 600 were not compiled yet. | |
| 601 This will report errors found during the compilation. | |
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602 |
| 19404 | 603 *:disa* *:disassemble* |
| 604 :disa[ssemble] {func} Show the instructions generated for {func}. | |
| 605 This is for debugging and testing. | |
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606 Note that for command line completion of {func} you |
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607 can prepend "s:" to find script-local functions. |
| 19404 | 608 |
| 21250 | 609 Limitations ~ |
| 610 | |
| 611 Local variables will not be visible to string evaluation. For example: > | |
| 612 def EvalString(): list<string> | |
| 613 let list = ['aa', 'bb', 'cc', 'dd'] | |
| 614 return range(1, 2)->map('list[v:val]') | |
| 615 enddef | |
| 616 | |
| 617 The map argument is a string expression, which is evaluated without the | |
| 618 function scope. Instead, use a lambda: > | |
| 619 def EvalString(): list<string> | |
| 620 let list = ['aa', 'bb', 'cc', 'dd'] | |
| 621 return range(1, 2)->map({ _, v -> list[v] }) | |
| 622 enddef | |
| 623 | |
| 624 | |
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625 ============================================================================== |
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626 |
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627 4. Types *vim9-types* |
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628 |
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629 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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630 |
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631 The following builtin types are supported: |
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632 bool |
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633 number |
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634 float |
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635 string |
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636 blob |
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637 list<{type}> |
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638 dict<{type}> |
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639 job |
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640 channel |
| 19646 | 641 func |
| 19968 | 642 func: {type} |
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643 func({type}, ...) |
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644 func({type}, ...): {type} |
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645 |
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646 Not supported yet: |
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647 tuple<a: {type}, b: {type}, ...> |
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648 |
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649 These types can be used in declarations, but no value will have this type: |
| 21499 | 650 {type}|{type} {not implemented yet} |
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651 void |
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652 any |
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653 |
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654 There is no array type, use list<{type}> instead. For a list constant an |
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655 efficient implementation is used that avoids allocating lot of small pieces of |
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656 memory. |
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657 |
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658 A partial and function can be declared in more or less specific ways: |
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659 func any kind of function reference, no type |
| 19968 | 660 checking for arguments or return value |
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661 func: {type} any number and type of arguments with specific |
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662 return type |
| 19968 | 663 func({type}) function with argument type, does not return |
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664 a value |
| 19968 | 665 func({type}): {type} function with argument type and return type |
| 666 func(?{type}) function with type of optional argument, does | |
| 667 not return a value | |
| 668 func(...{type}) function with type of variable number of | |
| 669 arguments, does not return a value | |
| 670 func({type}, ?{type}, ...{type}): {type} | |
| 671 function with: | |
| 672 - type of mandatory argument | |
| 673 - type of optional argument | |
| 674 - type of variable number of arguments | |
| 675 - return type | |
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676 |
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677 If the return type is "void" the function does not return a value. |
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678 |
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679 The reference can also be a |Partial|, in which case it stores extra arguments |
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680 and/or a dictionary, which are not visible to the caller. Since they are |
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681 called in the same way the declaration is the same. |
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682 |
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683 Custom types can be defined with `:type`: > |
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684 :type MyList list<string> |
|
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685 Custom types must start with a capital letter, to avoid name clashes with |
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686 builtin types added later, similarly to user functions. |
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687 {not implemented yet} |
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688 |
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689 And classes and interfaces can be used as types: > |
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690 :class MyClass |
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691 :let mine: MyClass |
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692 |
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693 :interface MyInterface |
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694 :let mine: MyInterface |
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695 |
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696 :class MyTemplate<Targ> |
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697 :let mine: MyTemplate<number> |
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698 :let mine: MyTemplate<string> |
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699 |
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700 :class MyInterface<Targ> |
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701 :let mine: MyInterface<number> |
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702 :let mine: MyInterface<string> |
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703 {not implemented yet} |
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704 |
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705 |
|
21717
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706 Variable types and type casting *variable-types* |
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707 |
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708 Variables declared in Vim9 script or in a `:def` function have a type, either |
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709 specified explicitly or inferred from the initialization. |
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710 |
|
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711 Global, buffer, window and tab page variables do not have a specific type, the |
|
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712 value can be changed at any time, possibly changing the type. Therefore, in |
|
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713 compiled code the "any" type is assumed. |
|
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714 |
|
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715 This can be a problem when the "any" type is undesired and the actual type is |
|
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716 expected to always be the same. For example, when declaring a list: > |
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717 let l: list<number> = [1, g:two] |
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718 This will give an error, because "g:two" has type "any". To avoid this, use a |
|
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719 type cast: > |
|
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720 let l: list<number> = [1, <number>g:two] |
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721 < *type-casting* |
|
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722 The compiled code will then check that "g:two" is a number at runtime and give |
|
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723 an error if it isn't. This is called type casting. |
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724 |
|
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725 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
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726 after the "<" or before the ">" (to avoid them being confused with |
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727 smaller-than and bigger-than operators). |
|
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728 |
|
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729 The semantics is that, if needed, a runtime type check is performed. The |
|
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730 value is not actually changed. If you need to change the type, e.g. to change |
|
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731 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
|
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732 string to a number. |
|
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733 |
|
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734 |
|
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735 Type inference *type-inference* |
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736 |
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737 In general: Whenever the type is clear it can be omitted. For example, when |
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738 declaring a variable and giving it a value: > |
| 22171 | 739 let var = 0 # infers number type |
| 740 let var = 'hello' # infers string type | |
|
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741 |
|
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742 The type of a list and dictionary comes from the common type of the values. |
|
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743 If the values all have the same type, that type is used for the list or |
|
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744 dictionary. If there is a mix of types, the "any" type is used. > |
|
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745 [1, 2, 3] list<number> |
|
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746 ['a', 'b', 'c'] list<string> |
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747 [1, 'x', 3] list<any> |
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748 |
| 21991 | 749 |
| 750 Stricter type checking *type-checking* | |
| 751 | |
| 752 In legacy Vim script, where a number was expected, a string would be | |
| 753 automatically converted to a number. This was convenient for an actual number | |
| 754 such as "123", but leads to unexpected problems (but no error message) if the | |
| 755 string doesn't start with a number. Quite often this leads to hard-to-find | |
| 756 bugs. | |
| 757 | |
| 758 In Vim9 script this has been made stricter. In most places it works just as | |
| 22171 | 759 before, if the value used matches the expected type. There will sometimes be |
| 760 an error, thus breaking backwards compatibility. For example: | |
| 21991 | 761 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
| 762 - Using a string value when setting a number options. | |
| 763 - Using a number where a string is expected. *E1024* | |
| 764 | |
|
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765 ============================================================================== |
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766 |
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767 5. Namespace, Import and Export |
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768 *vim9script* *vim9-export* *vim9-import* |
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769 |
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770 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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|
771 |
|
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772 A Vim9 script can be written to be imported. This means that everything in |
|
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773 the script is local, unless exported. Those exported items, and only those |
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774 items, can then be imported in another script. |
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775 |
| 21991 | 776 You can cheat by using the global namespace explicitly. We will assume here |
| 777 that you don't do that. | |
| 778 | |
|
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779 |
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780 Namespace ~ |
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781 *:vim9script* *:vim9* |
| 19303 | 782 To recognize a file that can be imported the `vim9script` statement must |
|
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783 appear as the first statement in the file. It tells Vim to interpret the |
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784 script in its own namespace, instead of the global namespace. If a file |
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785 starts with: > |
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786 vim9script |
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787 let myvar = 'yes' |
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788 Then "myvar" will only exist in this file. While without `vim9script` it would |
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789 be available as `g:myvar` from any other script and function. |
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790 |
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791 The variables at the file level are very much like the script-local "s:" |
| 20115 | 792 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
| 793 deleted. | |
|
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794 |
| 20115 | 795 In Vim9 script the global "g:" namespace can still be used as before. And the |
| 796 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
| 797 declared and they can be deleted. | |
|
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|
798 |
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|
799 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
|
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|
800 Vim default value, like with: > |
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801 :set cpo&vim |
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|
802 One of the effects is that |line-continuation| is always enabled. |
|
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803 The original value of 'cpoptions' is restored at the end of the script. |
|
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|
804 |
|
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|
805 |
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806 Export ~ |
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807 *:export* *:exp* |
| 21499 | 808 Exporting an item can be written as: > |
|
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809 export const EXPORTED_CONST = 1234 |
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810 export let someValue = ... |
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811 export def MyFunc() ... |
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812 export class MyClass ... |
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813 |
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814 As this suggests, only constants, variables, `:def` functions and classes can |
| 21499 | 815 be exported. {classes are not implemented yet} |
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816 |
| 20856 | 817 *E1042* |
| 818 `:export` can only be used in Vim9 script, at the script level. | |
|
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819 |
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820 |
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821 Import ~ |
| 20965 | 822 *:import* *:imp* *E1094* |
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823 The exported items can be imported individually in another Vim9 script: > |
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824 import EXPORTED_CONST from "thatscript.vim" |
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825 import MyClass from "myclass.vim" |
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826 |
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827 To import multiple items at the same time: > |
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828 import {someValue, MyClass} from "thatscript.vim" |
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829 |
| 19303 | 830 In case the name is ambiguous, another name can be specified: > |
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831 import MyClass as ThatClass from "myclass.vim" |
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832 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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833 |
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834 To import all exported items under a specific identifier: > |
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835 import * as That from 'thatscript.vim' |
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836 |
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837 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
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838 to choose the name "That", but it is highly recommended to use the name of the |
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839 script file to avoid confusion. |
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840 |
| 22171 | 841 `:import` can also be used in legacy Vim script. The imported items still |
| 842 become script-local, even when the "s:" prefix is not given. | |
| 843 | |
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844 The script name after `import` can be: |
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845 - A relative path, starting "." or "..". This finds a file relative to the |
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846 location of the script file itself. This is useful to split up a large |
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847 plugin into several files. |
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848 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
|
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849 will be rarely used. |
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850 - A path not being relative or absolute. This will be found in the |
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851 "import" subdirectories of 'runtimepath' entries. The name will usually be |
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852 longer and unique, to avoid loading the wrong file. |
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853 |
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854 Once a vim9 script file has been imported, the result is cached and used the |
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855 next time the same script is imported. It will not be read again. |
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856 *:import-cycle* |
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857 The `import` commands are executed when encountered. If that script (directly |
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858 or indirectly) imports the current script, then items defined after the |
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859 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
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860 result in undefined items. |
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861 |
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862 |
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863 Import in an autoload script ~ |
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864 |
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865 For optimal startup speed, loading scripts should be postponed until they are |
| 19303 | 866 actually needed. A recommended mechanism: |
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867 |
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868 1. In the plugin define user commands, functions and/or mappings that refer to |
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869 an autoload script. > |
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870 command -nargs=1 SearchForStuff call searchfor#Stuff(<f-args>) |
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871 |
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872 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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873 |
| 21825 | 874 2. In the autoload script do the actual work. You can import items from |
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875 other files to split up functionality in appropriate pieces. > |
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876 vim9script |
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877 import FilterFunc from "../import/someother.vim" |
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878 def searchfor#Stuff(arg: string) |
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879 let filtered = FilterFunc(arg) |
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880 ... |
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881 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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882 must be exactly the same as the prefix for the function name, that is how |
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883 Vim finds the file. |
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884 |
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885 3. Other functionality, possibly shared between plugins, contains the exported |
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886 items and any private items. > |
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887 vim9script |
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888 let localVar = 'local' |
| 22171 | 889 export def FilterFunc(arg: string): string |
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890 ... |
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891 < This goes in .../import/someother.vim. |
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892 |
|
21771
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893 When compiling a `:def` function and a function in an autoload script is |
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894 encountered, the script is not loaded until the `:def` function is called. |
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895 |
|
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896 |
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897 Import in legacy Vim script ~ |
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898 |
| 20856 | 899 If an `import` statement is used in legacy Vim script, the script-local "s:" |
| 900 namespace will be used for the imported item, even when "s:" is not specified. | |
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901 |
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902 |
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903 ============================================================================== |
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904 |
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905 9. Rationale *vim9-rationale* |
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906 |
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907 The :def command ~ |
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908 |
| 21825 | 909 Plugin writers have asked for a much faster Vim script. Investigations have |
| 19303 | 910 shown that keeping the existing semantics of function calls make this close to |
|
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911 impossible, because of the overhead involved with calling a function, setting |
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912 up the local function scope and executing lines. There are many details that |
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913 need to be handled, such as error messages and exceptions. The need to create |
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914 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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915 much overhead that cannot be avoided. |
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916 |
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917 Therefore the `:def` method to define a new-style function had to be added, |
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918 which allows for a function with different semantics. Most things still work |
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919 as before, but some parts do not. A new way to define a function was |
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920 considered the best way to separate the old-style code from Vim9 script code. |
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921 |
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922 Using "def" to define a function comes from Python. Other languages use |
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923 "function" which clashes with legacy Vim script. |
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924 |
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925 |
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926 Type checking ~ |
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927 |
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928 When compiling lines of Vim commands into instructions as much as possible |
|
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929 should be done at compile time. Postponing it to runtime makes the execution |
|
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930 slower and means mistakes are found only later. For example, when |
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931 encountering the "+" character and compiling this into a generic add |
|
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932 instruction, at execution time the instruction would have to inspect the type |
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933 of the arguments and decide what kind of addition to do. And when the |
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934 type is dictionary throw an error. If the types are known to be numbers then |
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935 an "add number" instruction can be used, which is faster. The error can be |
|
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936 given at compile time, no error handling is needed at runtime. |
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937 |
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938 The syntax for types is similar to Java, since it is easy to understand and |
| 21825 | 939 widely used. The type names are what were used in Vim before, with some |
|
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940 additions such as "void" and "bool". |
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941 |
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942 |
| 20856 | 943 Compiling functions early ~ |
| 944 | |
| 945 Functions are compiled when called or when `:defcompile` is used. Why not | |
| 946 compile them early, so that syntax and type errors are reported early? | |
| 947 | |
| 948 The functions can't be compiled right away when encountered, because there may | |
| 949 be forward references to functions defined later. Consider defining functions | |
| 950 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
| 951 to reorder the functions to avoid forward references. | |
| 952 | |
| 953 An alternative would be to first scan through the file to locate items and | |
| 20965 | 954 figure out their type, so that forward references are found, and only then |
| 20856 | 955 execute the script and compile the functions. This means the script has to be |
| 956 parsed twice, which is slower, and some conditions at the script level, such | |
| 957 as checking if a feature is supported, are hard to use. An attempt was made | |
| 958 to see if it works, but it turned out to be impossible to make work nicely. | |
| 959 | |
| 960 It would be possible to compile all the functions at the end of the script. | |
| 961 The drawback is that if a function never gets called, the overhead of | |
| 962 compiling it counts anyway. Since startup speed is very important, in most | |
| 963 cases it's better to do it later and accept that syntax and type errors are | |
| 964 only reported then. In case these errors should be found early, e.g. when | |
| 965 testing, the `:defcompile` command will help out. | |
| 966 | |
| 967 | |
| 968 TypeScript syntax and semantics ~ | |
|
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969 |
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970 Script writers have complained that the Vim script syntax is unexpectedly |
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971 different from what they are used to. To reduce this complaint popular |
| 20856 | 972 languages are used as an example. At the same time, we do not want to abandon |
| 973 the well-known parts of legacy Vim script. | |
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974 |
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975 Since Vim already uses `:let` and `:const` and optional type checking is |
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976 desirable, the JavaScript/TypeScript syntax fits best for variable |
| 22171 | 977 declarations: > |
| 978 const greeting = 'hello' # string type is inferred | |
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979 let name: string |
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980 ... |
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981 name = 'John' |
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982 |
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983 Expression evaluation was already close to what JavaScript and other languages |
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984 are doing. Some details are unexpected and can be fixed. For example how the |
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985 || and && operators work. Legacy Vim script: > |
|
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986 let value = 44 |
|
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987 ... |
|
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988 let result = value || 0 # result == 1 |
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989 |
| 21825 | 990 Vim9 script works like JavaScript/TypeScript, keep the value: > |
|
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991 let value = 44 |
|
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992 ... |
|
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993 let result = value || 0 # result == 44 |
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994 |
| 22171 | 995 There is no intention to completely match TypeScript syntax and semantics. We |
| 996 just want to take those parts that we can use for Vim and we expect Vim users | |
|
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997 will be happy with. TypeScript is a complex language with its own advantages |
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998 and disadvantages. To get an idea of the disadvantages read the book: |
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999 "JavaScript: The Good Parts". Or find the article "TypeScript: the good |
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1000 parts" and read the "Things to avoid" section. |
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1001 |
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1002 People used to other languages (Java, Python, etc.) will also find things in |
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1003 TypeScript that they do not like or do not understand. We'll try to avoid |
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1004 those things. |
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1005 |
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1006 Specific items from TypeScript we avoid: |
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1007 - Overloading "+", using it both for addition and string concatenation. This |
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1008 goes against legacy Vim script and often leads to mistakes. For that reason |
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1009 we will keep using ".." for string concatenation. Lua also uses ".." this |
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1010 way. And it allows for conversion to string for more values. |
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1011 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
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1012 cannot assign the value to a boolean. That is inconsistent and can be |
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1013 annoying. Vim recognizes an expression with && or || and allows using the |
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1014 result as a bool. |
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1015 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
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1016 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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1017 Falsy. |
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1018 - TypeScript has various "Readonly" types, which have limited usefulness, |
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1019 since a type cast can remove the immutable nature. Vim locks the value, |
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1020 which is more flexible, but is only checked at runtime. |
| 22171 | 1021 |
|
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1022 |
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1023 Import and Export ~ |
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1024 |
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1025 A problem of legacy Vim script is that by default all functions and variables |
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1026 are global. It is possible to make them script-local, but then they are not |
| 22171 | 1027 available in other scripts. This defies the concept of a package that only |
| 1028 exports selected items and keeps the rest local. | |
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1029 |
| 21825 | 1030 In Vim9 script a mechanism very similar to the JavaScript import and export |
|
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1031 mechanism is supported. It is a variant to the existing `:source` command |
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1032 that works like one would expect: |
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1033 - Instead of making everything global by default, everything is script-local, |
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1034 unless exported. |
| 22171 | 1035 - When importing a script the symbols that are imported are explicitly listed, |
| 1036 avoiding name conflicts and failures if functionality is added later. | |
|
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1037 - The mechanism allows for writing a big, long script with a very clear API: |
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1038 the exported function(s) and class(es). |
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1039 - By using relative paths loading can be much faster for an import inside of a |
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1040 package, no need to search many directories. |
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1041 - Once an import has been used, it can be cached and loading it again can be |
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1042 avoided. |
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1043 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1044 |
| 20856 | 1045 When sourcing a Vim9 script from a legacy script, only the items defined |
| 1046 globally can be used, not the exported items. Alternatives considered: | |
| 1047 - All the exported items become available as script-local items. This makes | |
| 22171 | 1048 it uncontrollable what items get defined and likely soon leads to trouble. |
| 20856 | 1049 - Use the exported items and make them global. Disadvantage is that it's then |
| 1050 not possible to avoid name clashes in the global namespace. | |
| 1051 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
| 1052 makes it difficult to use scripts for testing, or sourcing them from the | |
| 1053 command line to try them out. | |
| 22171 | 1054 Note that you can also use `:import` in legacy Vim script, see above. |
| 20856 | 1055 |
|
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1056 |
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1057 Classes ~ |
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1058 |
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1059 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
| 22171 | 1060 these interfaces have never become widespread. When Vim 9 was designed a |
| 1061 decision was made to phase out these interfaces and concentrate on Vim script, | |
| 1062 while encouraging plugin authors to write code in any language and run it as | |
| 1063 an external tool, using jobs and channels. | |
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1064 |
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1065 Still, using an external tool has disadvantages. An alternative is to convert |
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1066 the tool into Vim script. For that to be possible without too much |
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1067 translation, and keeping the code fast at the same time, the constructs of the |
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1068 tool need to be supported. Since most languages support classes the lack of |
| 22171 | 1069 support for classes in Vim is then a problem. |
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1070 |
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1071 Previously Vim supported a kind-of object oriented programming by adding |
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1072 methods to a dictionary. With some care this could be made to work, but it |
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1073 does not look like real classes. On top of that, it's very slow, because of |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
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1074 the use of dictionaries. |
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
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1075 |
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94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
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1076 The support of classes in Vim9 script is a "minimal common functionality" of |
| 22171 | 1077 class support in most languages. It works much like Java, which is the most |
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19181
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
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1078 popular programming language. |
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94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
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1079 |
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94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
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1080 |
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94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
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1081 |
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94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
Bram Moolenaar <Bram@vim.org>
parents:
diff
changeset
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1082 vim:tw=78:ts=8:noet:ft=help:norl: |