Mercurial > vim
annotate runtime/doc/vim9.txt @ 23088:285cde4b8d0e v8.2.2090
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Commit: https://github.com/vim/vim/commit/c5e6a7179d7dee4315b412b56e172bb1ff092d3e
Author: Bram Moolenaar <Bram@vim.org>
Date: Fri Dec 4 19:12:14 2020 +0100
patch 8.2.2090: Vim9: dict does not accept a key in quotes
Problem: Vim9: dict does not accept a key in quotes.
Solution: Recognize a key in single or double quotes.
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Fri, 04 Dec 2020 19:15:03 +0100 |
| parents | 29c5f168c6fd |
| children | 99ef85ff1af4 |
| rev | line source |
|---|---|
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1 *vim9.txt* For Vim version 8.2. Last change: 2020 Dec 04 |
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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 # |
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115 that starts a comment. |
| 20115 | 116 |
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117 |
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118 Vim9 functions ~ |
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119 |
| 20241 | 120 A function defined with `:def` is compiled. Execution is many times faster, |
| 121 often 10x to 100x times. | |
| 122 | |
| 20552 | 123 Many errors are already found when compiling, before the function is executed. |
| 20241 | 124 The syntax is strict, to enforce code that is easy to read and understand. |
| 125 | |
| 21991 | 126 Compilation is done when: |
| 127 - the function is first called | |
| 128 - when the `:defcompile` command is encountered in the script where the | |
| 129 function was defined | |
| 130 - `:disassemble` is used for the function. | |
| 131 - a function that is compiled calls the function or uses it as a function | |
| 132 reference | |
| 20552 | 133 |
| 134 `:def` has no options like `:function` does: "range", "abort", "dict" or | |
| 135 "closure". A `:def` function always aborts on an error, does not get a range | |
| 136 passed and cannot be a "dict" function. | |
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137 |
| 20241 | 138 The argument types and return type need to be specified. The "any" type can |
| 139 be used, type checking will then be done at runtime, like with legacy | |
| 140 functions. | |
| 141 | |
| 21825 | 142 Arguments are accessed by name, without "a:", just like any other language. |
| 143 There is no "a:" dictionary or "a:000" list. | |
| 20241 | 144 |
| 145 Variable arguments are defined as the last argument, with a name and have a | |
| 21825 | 146 list type, similar to TypeScript. For example, a list of numbers: > |
| 22171 | 147 def MyFunc(...itemlist: list<number>) |
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148 for item in itemlist |
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149 ... |
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150 |
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151 |
| 20241 | 152 Functions and variables are script-local by default ~ |
| 20856 | 153 *vim9-scopes* |
| 20115 | 154 When using `:function` or `:def` to specify a new function at the script level |
| 155 in a Vim9 script, the function is local to the script, as if "s:" was | |
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156 prefixed. Using the "s:" prefix is optional. To define a global function or |
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157 variable the "g:" prefix must be used. For functions in an autoload script |
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158 the "name#" prefix is sufficient. > |
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159 def ThisFunction() # script-local |
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160 def s:ThisFunction() # script-local |
| 22171 | 161 def g:ThatFunction() # global |
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162 def scriptname#function() # autoload |
| 20115 | 163 |
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164 When using `:function` or `:def` to specify a nested function inside a `:def` |
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165 function, this nested function is local to the code block it is defined in. |
| 22565 | 166 In a `:def` function it is not possible to define a script-local function. It |
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167 is possible to define a global function by using the "g:" prefix. |
| 20115 | 168 |
| 169 When referring to a function and no "s:" or "g:" prefix is used, Vim will | |
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170 search for the function: |
| 22565 | 171 - in the function scope, in block scopes |
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172 - in the script scope, possibly imported |
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173 - in the list of global functions |
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174 However, it is recommended to always use "g:" to refer to a global function |
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175 for clarity. |
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176 |
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177 In all cases the function must be defined before used. That is when it is |
| 22723 | 178 called, when `:defcompile` causes it to be compiled, or when code that calls |
| 179 it is being compiled (to figure out the return type). | |
| 20241 | 180 |
| 21676 | 181 The result is that functions and variables without a namespace can usually be |
| 20241 | 182 found in the script, either defined there or imported. Global functions and |
| 21676 | 183 variables could be defined anywhere (good luck finding out where!). |
| 20115 | 184 |
| 21825 | 185 Global functions can still be defined and deleted at nearly any time. In |
| 20317 | 186 Vim9 script script-local functions are defined once when the script is sourced |
| 20552 | 187 and cannot be deleted or replaced. |
| 20115 | 188 |
| 189 | |
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190 Variable declarations with :var, :final and :const ~ |
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191 *vim9-declaration* *:var* |
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192 Local variables need to be declared with `:var`. Local constants need to be |
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193 declared with `:final` or `:const`. We refer to both as "variables" in this |
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194 section. |
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195 |
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196 Variables can be local to a script, function or code block: > |
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197 vim9script |
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198 var script_var = 123 |
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199 def SomeFunc() |
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200 var func_var = script_var |
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201 if cond |
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202 var block_var = func_var |
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203 ... |
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204 |
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205 The variables are only visible in the block where they are defined and nested |
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206 blocks. Once the block ends the variable is no longer accessible: > |
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207 if cond |
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208 var inner = 5 |
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209 else |
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210 var inner = 0 |
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211 endif |
| 22171 | 212 echo inner # Error! |
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213 |
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214 The declaration must be done earlier: > |
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215 var inner: number |
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216 if cond |
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217 inner = 5 |
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218 else |
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219 inner = 0 |
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220 endif |
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221 echo inner |
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222 |
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223 To intentionally hide a variable from code that follows, a block can be |
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224 used: > |
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225 { |
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226 var temp = 'temp' |
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227 ... |
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228 } |
| 22171 | 229 echo temp # Error! |
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230 |
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231 Declaring a variable with a type but without an initializer will initialize to |
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232 zero, false or empty. |
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233 |
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234 In Vim9 script `:let` cannot be used. An existing variable is assigned to |
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235 without any command. The same for global, window, tab, buffer and Vim |
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236 variables, because they are not really declared. They can also be deleted |
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237 with `:unlet`. |
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238 |
| 21676 | 239 Variables and functions cannot shadow previously defined or imported variables |
| 240 and functions. | |
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241 Variables may shadow Ex commands, rename the variable if needed. |
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242 |
| 20241 | 243 Global variables and user defined functions must be prefixed with "g:", also |
| 244 at the script level. > | |
| 19968 | 245 vim9script |
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246 var script_local = 'text' |
| 21499 | 247 g:global = 'value' |
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248 var Funcref = g:ThatFunction |
| 19968 | 249 |
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250 Since `&opt = value` is now assigning a value to option "opt", ":&" cannot be |
|
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251 used to repeat a `:substitute` command. |
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252 |
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253 |
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254 Constants ~ |
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255 *vim9-const* *vim9-final* |
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256 How constants work varies between languages. Some consider a variable that |
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257 can't be assigned another value a constant. JavaScript is an example. Others |
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258 also make the value immutable, thus when a constant uses a list, the list |
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259 cannot be changed. In Vim9 we can use both. |
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260 |
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261 `:const` is used for making both the variable and the value a constant. Use |
|
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262 this for composite structures that you want to make sure will not be modified. |
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263 Example: > |
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264 const myList = [1, 2] |
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265 myList = [3, 4] # Error! |
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266 myList[0] = 9 # Error! |
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267 muList->add(3) # Error! |
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268 < *:final* |
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269 `:final` is used for making only the variable a constant, the value can be |
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270 changed. This is well known from Java. Example: > |
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271 final myList = [1, 2] |
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272 myList = [3, 4] # Error! |
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273 myList[0] = 9 # OK |
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274 muList->add(3) # OK |
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275 |
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276 It is common to write constants as ALL_CAPS, but you don't have to. |
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277 |
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278 The constant only applies to the value itself, not what it refers to. > |
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279 final females = ["Mary"] |
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280 const NAMES = [["John", "Peter"], females] |
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281 NAMES[0] = ["Jack"] # Error! |
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282 NAMES[0][0] = "Jack" # Error! |
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283 NAMES[1] = ["Emma"] # Error! |
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284 Names[1][0] = "Emma" # OK, now females[0] == "Emma" |
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285 |
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286 < *E1092* |
| 21499 | 287 Declaring more than one variable at a time, using the unpack notation, is |
| 288 currently not supported: > | |
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289 var [v1, v2] = GetValues() # Error! |
| 21499 | 290 That is because the type needs to be inferred from the list item type, which |
| 291 isn't that easy. | |
| 292 | |
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293 |
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294 Omitting :call and :eval ~ |
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295 |
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296 Functions can be called without `:call`: > |
| 22171 | 297 writefile(lines, 'file') |
| 19303 | 298 Using `:call` is still possible, but this is discouraged. |
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299 |
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300 A method call without `eval` is possible, so long as the start is an |
|
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301 identifier or can't be an Ex command. Examples: > |
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302 myList->add(123) |
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303 g:myList->add(123) |
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304 [1, 2, 3]->Process() |
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305 {a: 1, b: 2}->Process() |
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306 "foobar"->Process() |
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307 ("foobar")->Process() |
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308 'foobar'->Process() |
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309 ('foobar')->Process() |
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310 |
| 21825 | 311 In the rare case there is ambiguity between a function name and an Ex command, |
| 21676 | 312 prepend ":" to make clear you want to use the Ex command. For example, there |
| 313 is both the `:substitute` command and the `substitute()` function. When the | |
| 314 line starts with `substitute(` this will use the function. Prepend a colon to | |
| 315 use the command instead: > | |
|
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316 :substitute(pattern (replacement ( |
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317 |
|
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318 Note that while variables need to be defined before they can be used, |
| 21825 | 319 functions can be called before being defined. This is required to allow |
| 320 for cyclic dependencies between functions. It is slightly less efficient, | |
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321 since the function has to be looked up by name. And a typo in the function |
|
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322 name will only be found when the function is called. |
|
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323 |
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324 |
| 19968 | 325 Omitting function() ~ |
| 326 | |
| 327 A user defined function can be used as a function reference in an expression | |
| 328 without `function()`. The argument types and return type will then be checked. | |
| 329 The function must already have been defined. > | |
| 330 | |
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331 var Funcref = MyFunction |
| 19968 | 332 |
| 333 When using `function()` the resulting type is "func", a function with any | |
| 334 number of arguments and any return type. The function can be defined later. | |
| 335 | |
| 336 | |
|
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337 Automatic line continuation ~ |
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338 |
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339 In many cases it is obvious that an expression continues on the next line. In |
| 21676 | 340 those cases there is no need to prefix the line with a backslash |
| 341 |line-continuation|. For example, when a list spans multiple lines: > | |
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342 var mylist = [ |
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343 'one', |
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344 'two', |
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345 ] |
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346 And when a dict spans multiple lines: > |
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347 var mydict = { |
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348 one: 1, |
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349 two: 2, |
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350 } |
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351 Function call: > |
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352 var result = Func( |
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353 arg1, |
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354 arg2 |
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355 ) |
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356 |
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357 For binary operators in expressions not in [], {} or () a line break is |
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358 possible just before or after the operator. For example: > |
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359 var text = lead |
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360 .. middle |
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361 .. end |
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362 var total = start + |
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363 end - |
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364 correction |
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365 var result = positive |
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366 ? PosFunc(arg) |
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367 : NegFunc(arg) |
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368 |
| 21499 | 369 For a method call using "->" and a member using a dot, a line break is allowed |
| 370 before it: > | |
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371 var result = GetBuilder() |
| 20965 | 372 ->BuilderSetWidth(333) |
| 373 ->BuilderSetHeight(777) | |
| 374 ->BuilderBuild() | |
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375 var result = MyDict |
| 21499 | 376 .member |
| 20965 | 377 |
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378 < *E1050* |
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379 To make it possible for the operator at the start of the line to be |
| 21250 | 380 recognized, it is required to put a colon before a range. This will add |
|
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381 "start" and print: > |
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382 var result = start |
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383 + print |
| 21250 | 384 Like this: > |
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385 var result = start + print |
| 21250 | 386 |
|
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387 This will assign "start" and print a line: > |
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388 var result = start |
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389 :+ print |
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390 |
| 23047 | 391 Note that the colon is not required for the |+cmd| argument: > |
| 392 edit +6 fname | |
| 393 | |
|
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394 It is also possible to split a function header over multiple lines, in between |
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395 arguments: > |
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396 def MyFunc( |
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397 text: string, |
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398 separator = '-' |
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399 ): string |
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400 |
| 21250 | 401 Notes: |
| 402 - "enddef" cannot be used at the start of a continuation line, it ends the | |
| 403 current function. | |
| 404 - No line break is allowed in the LHS of an assignment. Specifically when | |
| 405 unpacking a list |:let-unpack|. This is OK: > | |
| 22171 | 406 [var1, var2] = |
| 21250 | 407 Func() |
| 408 < This does not work: > | |
| 22171 | 409 [var1, |
| 21250 | 410 var2] = |
| 411 Func() | |
| 412 - No line break is allowed in between arguments of an `:echo`, `:execute` and | |
| 413 similar commands. This is OK: > | |
| 22171 | 414 echo [1, |
| 21250 | 415 2] [3, |
| 416 4] | |
| 417 < This does not work: > | |
| 22171 | 418 echo [1, 2] |
| 21250 | 419 [3, 4] |
| 420 - No line break is allowed in the arguments of a lambda, between the "{" and | |
| 421 "->". This is OK: > | |
| 22171 | 422 filter(list, {k, v -> |
| 21250 | 423 v > 0}) |
| 424 < This does not work: > | |
| 22171 | 425 filter(list, {k, |
| 21250 | 426 v -> v > 0}) |
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427 |
|
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428 |
|
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429 No curly braces expansion ~ |
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430 |
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431 |curly-braces-names| cannot be used. |
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432 |
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433 |
|
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434 Dictionary literals ~ |
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435 |
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436 Traditionally Vim has supported dictionary literals with a {} syntax: > |
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437 let dict = {'key': value} |
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438 |
|
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439 Later it became clear that using a simple text key is very common, thus |
|
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440 literal dictionaries were introduced in a backwards compatible way: > |
|
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441 let dict = #{key: value} |
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442 |
|
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443 However, this #{} syntax is unlike any existing language. As it turns out |
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444 that using a literal key is much more common than using an expression, and |
|
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445 considering that JavaScript uses this syntax, using the {} form for dictionary |
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446 literals is considered a much more useful syntax. In Vim9 script the {} form |
|
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447 uses literal keys: > |
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448 let dict = {key: value} |
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449 |
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450 This works for alphanumeric characters, underscore and dash. If you want to |
|
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451 use another character, use a single or double quoted string: > |
|
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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452 let dict = {'key with space': value} |
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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453 let dict = {"key\twith\ttabs": value} |
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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454 let dict = {'': value} # empty key |
|
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455 |
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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456 In case the key needs to be an expression, square brackets can be used, just |
|
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patch 8.2.2090: Vim9: dict does not accept a key in quotes
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457 like in JavaScript: > |
|
22936
00b0275ffe7f
patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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458 let dict = {["key" .. nr]: value} |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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459 |
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patch 8.2.2015: Vim9: literal dict #{} is not like any other language
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460 |
|
21584
d0c76ce48326
patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
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461 No :xit, :t, :append, :change or :insert ~ |
| 19303 | 462 |
|
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patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
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463 These commands are too easily confused with local variable names. |
|
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patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
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464 Instead of `:x` or `:xit` you can use `:exit`. |
|
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patch 8.2.1342: Vim9: accidentally using "t" gives a confusing error
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465 Instead of `:t` you can use `:copy`. |
|
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patch 8.2.0149: maintaining a Vim9 branch separately is more work
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466 |
| 19303 | 467 |
| 468 Comparators ~ | |
| 469 | |
| 470 The 'ignorecase' option is not used for comparators that use strings. | |
|
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471 |
|
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472 |
|
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473 White space ~ |
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474 |
|
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changeset
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475 Vim9 script enforces proper use of white space. This is no longer allowed: > |
|
22391
a9fb7efa31d6
patch 8.2.1744: Vim9: using ":const!" is weird
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476 var name=234 # Error! |
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patch 8.2.1744: Vim9: using ":const!" is weird
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477 var name= 234 # Error! |
|
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478 var name =234 # Error! |
|
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479 There must be white space before and after the "=": > |
|
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480 var name = 234 # OK |
| 21250 | 481 White space must also be put before the # that starts a comment after a |
| 482 command: > | |
|
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483 var name = 234# Error! |
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484 var name = 234 # OK |
|
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485 |
|
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486 White space is required around most operators. |
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487 |
|
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488 White space is not allowed: |
|
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489 - Between a function name and the "(": > |
| 22171 | 490 call Func (arg) # Error! |
| 491 call Func | |
| 492 \ (arg) # Error! | |
| 493 call Func(arg) # OK | |
| 494 call Func( | |
| 495 \ arg) # OK | |
| 496 call Func( | |
| 497 \ arg # OK | |
|
19473
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patch 8.2.0294: cannot use Ex command that is also a function name
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498 \ ) |
|
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499 |
|
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500 |
|
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501 Conditions and expressions ~ |
|
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502 |
|
22500
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patch 8.2.1798: Vim9: trinary operator condition is too permissive
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503 Conditions and expressions are mostly working like they do in other languages. |
|
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504 Some values are different from legacy Vim script: |
|
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505 value legacy Vim script Vim9 script ~ |
|
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506 0 falsy falsy |
|
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507 1 truthy truthy |
|
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508 99 truthy Error! |
|
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509 "0" falsy Error! |
|
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510 "99" truthy Error! |
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511 "text" falsy Error! |
|
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512 |
|
22500
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513 For the "??" operator and when using "!" then there is no error, every value |
|
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514 is either falsy or truthy. This is mostly like JavaScript, except that an |
|
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515 empty list and dict is falsy: |
|
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516 |
|
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517 type truthy when ~ |
|
22272
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patch 8.2.1685: Vim9: cannot declare a constant value
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518 bool v:true or 1 |
|
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519 number non-zero |
|
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|
520 float non-zero |
|
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|
521 string non-empty |
|
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|
522 blob non-empty |
|
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523 list non-empty (different from JavaScript) |
|
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|
524 dictionary non-empty (different from JavaScript) |
| 19968 | 525 func when there is a function name |
|
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|
526 special v:true |
|
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|
527 job when not NULL |
|
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|
528 channel when not NULL |
|
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|
529 class when not NULL |
|
94eda51ba9ba
patch 8.2.0149: maintaining a Vim9 branch separately is more work
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|
530 object when not NULL (TODO: when isTrue() returns v:true) |
|
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parents:
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|
531 |
|
22494
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
532 The boolean operators "||" and "&&" expect the values to be boolean, zero or |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
533 one: > |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
534 1 || false == true |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
535 0 || 1 == true |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
536 0 || false == false |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
537 1 && true == true |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
538 0 && 1 == false |
|
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patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
539 8 || 0 Error! |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
540 'yes' && 0 Error! |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
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|
541 [] || 99 Error! |
|
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|
542 |
|
22494
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patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
543 When using "!" for inverting, there is no error for using any type and the |
|
22500
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patch 8.2.1798: Vim9: trinary operator condition is too permissive
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changeset
|
544 result is a boolean. "!!" can be used to turn any value into boolean: > |
|
22494
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patch 8.2.1795: Vim9: operators && and || have a confusing result
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changeset
|
545 !'yes' == false |
|
22500
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changeset
|
546 !![] == false |
|
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|
547 !![1, 2, 3] == true |
|
22494
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changeset
|
548 |
|
4c21f7f6f9e3
patch 8.2.1795: Vim9: operators && and || have a confusing result
Bram Moolenaar <Bram@vim.org>
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changeset
|
549 When using "`.."` for string concatenation arguments of simple types are |
|
22500
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patch 8.2.1798: Vim9: trinary operator condition is too permissive
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changeset
|
550 always converted to string: > |
|
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|
551 'hello ' .. 123 == 'hello 123' |
| 21825 | 552 'hello ' .. v:true == 'hello v:true' |
|
19181
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|
553 |
|
21771
fcf978444298
patch 8.2.1435: Vim9: always converting to string for ".." leads to mistakes
Bram Moolenaar <Bram@vim.org>
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21717
diff
changeset
|
554 Simple types are string, float, special and bool. For other types |string()| |
|
fcf978444298
patch 8.2.1435: Vim9: always converting to string for ".." leads to mistakes
Bram Moolenaar <Bram@vim.org>
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21717
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changeset
|
555 can be used. |
| 22171 | 556 *false* *true* |
|
19181
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|
557 In Vim9 script one can use "true" for v:true and "false" for v:false. |
|
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|
558 |
| 21825 | 559 Indexing a string with [idx] or [idx, idx] uses character indexes instead of |
| 560 byte indexes. Example: > | |
| 561 echo 'bár'[1] | |
| 562 In legacy script this results in the character 0xc3 (an illegal byte), in Vim9 | |
| 563 script this results in the string 'á'. | |
| 564 | |
|
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|
565 |
| 21093 | 566 What to watch out for ~ |
| 567 *vim9-gotchas* | |
| 568 Vim9 was designed to be closer to often used programming languages, but at the | |
| 569 same time tries to support the legacy Vim commands. Some compromises had to | |
| 570 be made. Here is a summary of what might be unexpected. | |
| 571 | |
| 572 Ex command ranges need to be prefixed with a colon. > | |
| 22171 | 573 -> # legacy Vim: shifts the previous line to the right |
| 574 ->func() # Vim9: method call in continuation line | |
| 575 :-> # Vim9: shifts the previous line to the right | |
| 21093 | 576 |
| 22171 | 577 %s/a/b # legacy Vim: substitute on all lines |
| 21093 | 578 x = alongname |
| 22171 | 579 % another # Vim9: line continuation without a backslash |
| 580 :%s/a/b # Vim9: substitute on all lines | |
| 581 'text'->func() # Vim9: method call | |
| 582 :'t # legacy Vim: jump to mark m | |
| 21093 | 583 |
| 21676 | 584 Some Ex commands can be confused with assignments in Vim9 script: > |
| 585 g:name = value # assignment | |
| 586 g:pattern:cmd # invalid command - ERROR | |
| 587 :g:pattern:cmd # :global command | |
| 588 | |
| 21093 | 589 Functions defined with `:def` compile the whole function. Legacy functions |
| 590 can bail out, and the following lines are not parsed: > | |
| 591 func Maybe() | |
| 592 if !has('feature') | |
| 593 return | |
| 594 endif | |
| 595 use-feature | |
| 596 endfunc | |
| 597 Vim9 functions are compiled as a whole: > | |
| 598 def Maybe() | |
| 599 if !has('feature') | |
| 600 return | |
| 601 endif | |
| 22171 | 602 use-feature # May give compilation error |
| 21093 | 603 enddef |
| 604 For a workaround, split it in two functions: > | |
| 605 func Maybe() | |
| 606 if has('feature') | |
| 607 call MaybyInner() | |
| 608 endif | |
| 609 endfunc | |
| 610 if has('feature') | |
| 611 def MaybeInner() | |
| 612 use-feature | |
| 613 enddef | |
| 614 endif | |
| 22171 | 615 Or put the unsupported code inside an `if` with a constant expression that |
| 21991 | 616 evaluates to false: > |
| 617 def Maybe() | |
| 618 if has('feature') | |
| 619 use-feature | |
| 620 endif | |
| 621 enddef | |
| 622 Note that for unrecognized commands there is no check for "|" and a following | |
| 623 command. This will give an error for missing `endif`: > | |
| 624 def Maybe() | |
| 625 if has('feature') | use-feature | endif | |
| 626 enddef | |
| 21093 | 627 |
|
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628 ============================================================================== |
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629 |
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630 3. New style functions *fast-functions* |
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631 |
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632 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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633 |
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634 *:def* |
| 21825 | 635 :def[!] {name}([arguments])[: {return-type}] |
|
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636 Define a new function by the name {name}. The body of |
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637 the function follows in the next lines, until the |
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638 matching `:enddef`. |
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639 |
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640 When {return-type} is omitted or is "void" the |
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641 function is not expected to return anything. |
|
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642 |
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643 {arguments} is a sequence of zero or more argument |
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644 declarations. There are three forms: |
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645 {name}: {type} |
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646 {name} = {value} |
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647 {name}: {type} = {value} |
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648 The first form is a mandatory argument, the caller |
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649 must always provide them. |
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650 The second and third form are optional arguments. |
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651 When the caller omits an argument the {value} is used. |
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652 |
| 20856 | 653 The function will be compiled into instructions when |
| 21499 | 654 called, or when `:disassemble` or `:defcompile` is |
| 655 used. Syntax and type errors will be produced at that | |
| 656 time. | |
| 20856 | 657 |
| 21499 | 658 It is possible to nest `:def` inside another `:def` or |
| 659 `:function` up to about 50 levels deep. | |
| 19303 | 660 |
|
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661 [!] is used as with `:function`. Note that |
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662 script-local functions cannot be deleted or redefined |
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663 later in Vim9 script. They can only be removed by |
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664 reloading the same script. |
|
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665 |
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666 *:enddef* |
| 21499 | 667 :enddef End of a function defined with `:def`. It should be on |
| 668 a line by its own. | |
|
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669 |
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670 |
|
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671 If the script the function is defined in is Vim9 script, then script-local |
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672 variables can be accessed without the "s:" prefix. They must be defined |
| 20856 | 673 before the function is compiled. If the script the function is defined in is |
| 674 legacy script, then script-local variables must be accessed with the "s:" | |
| 21991 | 675 prefix and they do not need to exist (they can be deleted any time). |
|
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676 |
| 20552 | 677 *:defc* *:defcompile* |
| 678 :defc[ompile] Compile functions defined in the current script that | |
| 679 were not compiled yet. | |
| 680 This will report errors found during the compilation. | |
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681 |
| 19404 | 682 *:disa* *:disassemble* |
| 683 :disa[ssemble] {func} Show the instructions generated for {func}. | |
| 684 This is for debugging and testing. | |
|
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685 Note that for command line completion of {func} you |
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686 can prepend "s:" to find script-local functions. |
| 19404 | 687 |
| 21250 | 688 Limitations ~ |
| 689 | |
| 690 Local variables will not be visible to string evaluation. For example: > | |
| 691 def EvalString(): list<string> | |
|
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692 var list = ['aa', 'bb', 'cc', 'dd'] |
| 21250 | 693 return range(1, 2)->map('list[v:val]') |
| 694 enddef | |
| 695 | |
| 696 The map argument is a string expression, which is evaluated without the | |
| 697 function scope. Instead, use a lambda: > | |
| 698 def EvalString(): list<string> | |
|
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699 var list = ['aa', 'bb', 'cc', 'dd'] |
| 21250 | 700 return range(1, 2)->map({ _, v -> list[v] }) |
| 701 enddef | |
| 702 | |
| 703 | |
|
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704 ============================================================================== |
|
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705 |
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706 4. Types *vim9-types* |
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707 |
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708 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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|
709 |
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710 The following builtin types are supported: |
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711 bool |
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712 number |
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713 float |
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714 string |
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715 blob |
|
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716 list<{type}> |
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717 dict<{type}> |
|
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718 job |
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|
719 channel |
| 19646 | 720 func |
| 19968 | 721 func: {type} |
|
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722 func({type}, ...) |
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723 func({type}, ...): {type} |
|
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724 |
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725 Not supported yet: |
|
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726 tuple<a: {type}, b: {type}, ...> |
|
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727 |
|
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|
728 These types can be used in declarations, but no value will have this type: |
| 21499 | 729 {type}|{type} {not implemented yet} |
|
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|
730 void |
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|
731 any |
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|
732 |
|
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|
733 There is no array type, use list<{type}> instead. For a list constant an |
|
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734 efficient implementation is used that avoids allocating lot of small pieces of |
|
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|
735 memory. |
|
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|
736 |
|
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|
737 A partial and function can be declared in more or less specific ways: |
|
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|
738 func any kind of function reference, no type |
| 19968 | 739 checking for arguments or return value |
|
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740 func: {type} any number and type of arguments with specific |
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|
741 return type |
| 19968 | 742 func({type}) function with argument type, does not return |
|
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|
743 a value |
| 19968 | 744 func({type}): {type} function with argument type and return type |
| 745 func(?{type}) function with type of optional argument, does | |
| 746 not return a value | |
| 747 func(...{type}) function with type of variable number of | |
| 748 arguments, does not return a value | |
| 749 func({type}, ?{type}, ...{type}): {type} | |
| 750 function with: | |
| 751 - type of mandatory argument | |
| 752 - type of optional argument | |
| 753 - type of variable number of arguments | |
| 754 - return type | |
|
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|
755 |
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|
756 If the return type is "void" the function does not return a value. |
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|
757 |
|
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|
758 The reference can also be a |Partial|, in which case it stores extra arguments |
|
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|
759 and/or a dictionary, which are not visible to the caller. Since they are |
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|
760 called in the same way the declaration is the same. |
|
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|
761 |
|
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|
762 Custom types can be defined with `:type`: > |
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763 :type MyList list<string> |
|
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764 Custom types must start with a capital letter, to avoid name clashes with |
|
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|
765 builtin types added later, similarly to user functions. |
|
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|
766 {not implemented yet} |
|
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767 |
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|
768 And classes and interfaces can be used as types: > |
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769 :class MyClass |
|
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770 :var mine: MyClass |
|
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|
771 |
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772 :interface MyInterface |
|
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773 :var mine: MyInterface |
|
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|
774 |
|
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775 :class MyTemplate<Targ> |
|
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776 :var mine: MyTemplate<number> |
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777 :var mine: MyTemplate<string> |
|
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|
778 |
|
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779 :class MyInterface<Targ> |
|
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780 :var mine: MyInterface<number> |
|
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781 :var mine: MyInterface<string> |
|
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782 {not implemented yet} |
|
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|
783 |
|
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784 |
|
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785 Variable types and type casting ~ |
|
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|
786 *variable-types* |
|
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787 Variables declared in Vim9 script or in a `:def` function have a type, either |
|
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788 specified explicitly or inferred from the initialization. |
|
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789 |
|
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790 Global, buffer, window and tab page variables do not have a specific type, the |
|
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791 value can be changed at any time, possibly changing the type. Therefore, in |
|
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792 compiled code the "any" type is assumed. |
|
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|
793 |
|
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|
794 This can be a problem when the "any" type is undesired and the actual type is |
|
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795 expected to always be the same. For example, when declaring a list: > |
|
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796 var l: list<number> = [1, g:two] |
|
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797 This will give an error, because "g:two" has type "any". To avoid this, use a |
|
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798 type cast: > |
|
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799 var l: list<number> = [1, <number>g:two] |
|
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800 < *type-casting* |
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801 The compiled code will then check that "g:two" is a number at runtime and give |
|
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802 an error if it isn't. This is called type casting. |
|
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|
803 |
|
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804 The syntax of a type cast is: "<" {type} ">". There cannot be white space |
|
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805 after the "<" or before the ">" (to avoid them being confused with |
|
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|
806 smaller-than and bigger-than operators). |
|
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807 |
|
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808 The semantics is that, if needed, a runtime type check is performed. The |
|
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809 value is not actually changed. If you need to change the type, e.g. to change |
|
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810 it to a string, use the |string()| function. Or use |str2nr()| to convert a |
|
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811 string to a number. |
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812 |
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813 |
|
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814 Type inference ~ |
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815 *type-inference* |
|
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816 In general: Whenever the type is clear it can be omitted. For example, when |
|
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817 declaring a variable and giving it a value: > |
|
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818 var name = 0 # infers number type |
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819 var name = 'hello' # infers string type |
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820 |
|
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821 The type of a list and dictionary comes from the common type of the values. |
|
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822 If the values all have the same type, that type is used for the list or |
|
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823 dictionary. If there is a mix of types, the "any" type is used. > |
|
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824 [1, 2, 3] list<number> |
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825 ['a', 'b', 'c'] list<string> |
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826 [1, 'x', 3] list<any> |
|
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827 |
| 21991 | 828 |
|
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829 Stricter type checking ~ |
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830 *type-checking* |
| 21991 | 831 In legacy Vim script, where a number was expected, a string would be |
| 832 automatically converted to a number. This was convenient for an actual number | |
| 833 such as "123", but leads to unexpected problems (but no error message) if the | |
| 834 string doesn't start with a number. Quite often this leads to hard-to-find | |
| 835 bugs. | |
| 836 | |
| 837 In Vim9 script this has been made stricter. In most places it works just as | |
| 22171 | 838 before, if the value used matches the expected type. There will sometimes be |
| 839 an error, thus breaking backwards compatibility. For example: | |
| 21991 | 840 - Using a number other than 0 or 1 where a boolean is expected. *E1023* |
| 841 - Using a string value when setting a number options. | |
| 842 - Using a number where a string is expected. *E1024* | |
| 843 | |
|
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844 ============================================================================== |
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845 |
|
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846 5. Namespace, Import and Export |
|
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847 *vim9script* *vim9-export* *vim9-import* |
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848 |
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849 THIS IS STILL UNDER DEVELOPMENT - ANYTHING CAN BREAK - ANYTHING CAN CHANGE |
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850 |
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851 A Vim9 script can be written to be imported. This means that everything in |
|
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852 the script is local, unless exported. Those exported items, and only those |
|
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853 items, can then be imported in another script. |
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854 |
| 21991 | 855 You can cheat by using the global namespace explicitly. We will assume here |
| 856 that you don't do that. | |
| 857 | |
|
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858 |
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859 Namespace ~ |
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860 *:vim9script* *:vim9* |
| 19303 | 861 To recognize a file that can be imported the `vim9script` statement must |
|
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862 appear as the first statement in the file. It tells Vim to interpret the |
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863 script in its own namespace, instead of the global namespace. If a file |
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864 starts with: > |
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865 vim9script |
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866 var myvar = 'yes' |
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867 Then "myvar" will only exist in this file. While without `vim9script` it would |
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868 be available as `g:myvar` from any other script and function. |
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869 |
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870 The variables at the file level are very much like the script-local "s:" |
| 20115 | 871 variables in legacy Vim script, but the "s:" is omitted. And they cannot be |
| 872 deleted. | |
|
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873 |
| 20115 | 874 In Vim9 script the global "g:" namespace can still be used as before. And the |
| 875 "w:", "b:" and "t:" namespaces. These have in common that variables are not | |
| 876 declared and they can be deleted. | |
|
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|
877 |
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878 A side effect of `:vim9script` is that the 'cpoptions' option is set to the |
|
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879 Vim default value, like with: > |
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880 :set cpo&vim |
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881 One of the effects is that |line-continuation| is always enabled. |
|
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882 The original value of 'cpoptions' is restored at the end of the script. |
|
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883 |
|
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|
884 |
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885 Export ~ |
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886 *:export* *:exp* |
| 21499 | 887 Exporting an item can be written as: > |
|
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888 export const EXPORTED_CONST = 1234 |
|
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889 export var someValue = ... |
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|
890 export final someValue = ... |
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891 export const someValue = ... |
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892 export def MyFunc() ... |
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893 export class MyClass ... |
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894 |
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895 As this suggests, only constants, variables, `:def` functions and classes can |
| 21499 | 896 be exported. {classes are not implemented yet} |
|
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897 |
| 20856 | 898 *E1042* |
| 899 `:export` can only be used in Vim9 script, at the script level. | |
|
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900 |
|
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|
901 |
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902 Import ~ |
| 20965 | 903 *:import* *:imp* *E1094* |
|
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904 The exported items can be imported individually in another Vim9 script: > |
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905 import EXPORTED_CONST from "thatscript.vim" |
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906 import MyClass from "myclass.vim" |
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907 |
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908 To import multiple items at the same time: > |
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909 import {someValue, MyClass} from "thatscript.vim" |
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910 |
| 19303 | 911 In case the name is ambiguous, another name can be specified: > |
|
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912 import MyClass as ThatClass from "myclass.vim" |
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913 import {someValue, MyClass as ThatClass} from "myclass.vim" |
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914 |
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915 To import all exported items under a specific identifier: > |
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916 import * as That from 'thatscript.vim' |
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917 |
| 22328 | 918 {not implemented yet: using "This as That"} |
| 919 | |
|
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920 Then you can use "That.EXPORTED_CONST", "That.someValue", etc. You are free |
|
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921 to choose the name "That", but it is highly recommended to use the name of the |
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922 script file to avoid confusion. |
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923 |
| 22171 | 924 `:import` can also be used in legacy Vim script. The imported items still |
| 925 become script-local, even when the "s:" prefix is not given. | |
| 926 | |
|
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927 The script name after `import` can be: |
|
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928 - A relative path, starting "." or "..". This finds a file relative to the |
|
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929 location of the script file itself. This is useful to split up a large |
|
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930 plugin into several files. |
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931 - An absolute path, starting with "/" on Unix or "D:/" on MS-Windows. This |
| 22723 | 932 will rarely be used. |
|
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933 - A path not being relative or absolute. This will be found in the |
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|
934 "import" subdirectories of 'runtimepath' entries. The name will usually be |
|
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935 longer and unique, to avoid loading the wrong file. |
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936 |
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937 Once a vim9 script file has been imported, the result is cached and used the |
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938 next time the same script is imported. It will not be read again. |
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|
939 *:import-cycle* |
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940 The `import` commands are executed when encountered. If that script (directly |
|
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941 or indirectly) imports the current script, then items defined after the |
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942 `import` won't be processed yet. Therefore cyclic imports can exist, but may |
|
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943 result in undefined items. |
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944 |
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945 |
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946 Import in an autoload script ~ |
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947 |
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948 For optimal startup speed, loading scripts should be postponed until they are |
| 19303 | 949 actually needed. A recommended mechanism: |
|
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950 |
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951 1. In the plugin define user commands, functions and/or mappings that refer to |
|
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952 an autoload script. > |
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953 command -nargs=1 SearchForStuff call searchfor#Stuff(<f-args>) |
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954 |
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955 < This goes in .../plugin/anyname.vim. "anyname.vim" can be freely chosen. |
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956 |
| 21825 | 957 2. In the autoload script do the actual work. You can import items from |
|
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958 other files to split up functionality in appropriate pieces. > |
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959 vim9script |
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960 import FilterFunc from "../import/someother.vim" |
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961 def searchfor#Stuff(arg: string) |
|
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962 var filtered = FilterFunc(arg) |
|
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963 ... |
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964 < This goes in .../autoload/searchfor.vim. "searchfor" in the file name |
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965 must be exactly the same as the prefix for the function name, that is how |
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966 Vim finds the file. |
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967 |
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968 3. Other functionality, possibly shared between plugins, contains the exported |
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969 items and any private items. > |
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970 vim9script |
|
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|
971 var localVar = 'local' |
| 22171 | 972 export def FilterFunc(arg: string): string |
|
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973 ... |
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974 < This goes in .../import/someother.vim. |
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975 |
|
21771
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|
976 When compiling a `:def` function and a function in an autoload script is |
|
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|
977 encountered, the script is not loaded until the `:def` function is called. |
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|
978 |
|
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979 |
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980 Import in legacy Vim script ~ |
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981 |
| 20856 | 982 If an `import` statement is used in legacy Vim script, the script-local "s:" |
| 983 namespace will be used for the imported item, even when "s:" is not specified. | |
|
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984 |
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985 |
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|
986 ============================================================================== |
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987 |
| 22328 | 988 6. Future work: classes *vim9-classes* |
| 989 | |
| 990 Above "class" was mentioned a few times, but it has not been implemented yet. | |
|
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991 Most of Vim9 script can be created without this functionality, and since |
| 22328 | 992 implementing classes is going to be a lot of work, it is left for the future. |
| 993 For now we'll just make sure classes can be added later. | |
| 994 | |
| 995 Thoughts: | |
| 996 - `class` / `endclass`, everything in one file | |
| 997 - Class names are always CamelCase | |
| 998 - Single constructor | |
| 999 - Single inheritance with `class ThisClass extends BaseClass` | |
| 1000 - `abstract class` | |
| 1001 - `interface` (Abstract class without any implementation) | |
| 1002 - `class SomeClass implements SomeInterface` | |
| 1003 - Generics for class: `class <Tkey, Tentry>` | |
| 1004 - Generics for function: `def <Tkey> GetLast(key: Tkey)` | |
| 1005 | |
| 1006 Again, much of this is from TypeScript. | |
| 1007 | |
| 1008 Some things that look like good additions: | |
| 1009 - Use a class as an interface (like Dart) | |
| 1010 - Extend a class with methods, using an import (like Dart) | |
| 1011 | |
| 1012 An important class that will be provided is "Promise". Since Vim is single | |
| 1013 threaded, connecting asynchronous operations is a natural way of allowing | |
| 1014 plugins to do their work without blocking the user. It's a uniform way to | |
| 1015 invoke callbacks and handle timeouts and errors. | |
| 1016 | |
| 1017 ============================================================================== | |
| 1018 | |
|
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1019 9. Rationale *vim9-rationale* |
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1020 |
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1021 The :def command ~ |
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1022 |
|
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1023 Plugin writers have asked for much faster Vim script. Investigations have |
| 19303 | 1024 shown that keeping the existing semantics of function calls make this close to |
|
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1025 impossible, because of the overhead involved with calling a function, setting |
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1026 up the local function scope and executing lines. There are many details that |
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1027 need to be handled, such as error messages and exceptions. The need to create |
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1028 a dictionary for a: and l: scopes, the a:000 list and several others add too |
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1029 much overhead that cannot be avoided. |
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1030 |
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1031 Therefore the `:def` method to define a new-style function had to be added, |
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1032 which allows for a function with different semantics. Most things still work |
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1033 as before, but some parts do not. A new way to define a function was |
|
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1034 considered the best way to separate the legacy style code from Vim9 style code. |
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1035 |
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1036 Using "def" to define a function comes from Python. Other languages use |
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1037 "function" which clashes with legacy Vim script. |
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1038 |
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1039 |
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1040 Type checking ~ |
|
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1041 |
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1042 When compiling lines of Vim commands into instructions as much as possible |
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1043 should be done at compile time. Postponing it to runtime makes the execution |
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1044 slower and means mistakes are found only later. For example, when |
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1045 encountering the "+" character and compiling this into a generic add |
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1046 instruction, at execution time the instruction would have to inspect the type |
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1047 of the arguments and decide what kind of addition to do. And when the |
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1048 type is dictionary throw an error. If the types are known to be numbers then |
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1049 an "add number" instruction can be used, which is faster. The error can be |
|
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1050 given at compile time, no error handling is needed at runtime, since adding |
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1051 two numbers cannot fail. |
|
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1052 |
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1053 The syntax for types, using <type> for compound types, is similar to Java. It |
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1054 is easy to understand and widely used. The type names are what were used in |
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1055 Vim before, with some additions such as "void" and "bool". |
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1056 |
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1057 |
| 22328 | 1058 Removing clutter and weirdness ~ |
| 20856 | 1059 |
| 22328 | 1060 Once decided that `:def` functions have different syntax than legacy functions, |
| 1061 we are free to add improvements to make the code more familiar for users who | |
| 1062 know popular programming languages. In other words: remove weird things that | |
|
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1063 only Vim does. |
| 22328 | 1064 |
| 1065 We can also remove clutter, mainly things that were done to make Vim script | |
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1066 backwards compatible with the good old Vi commands. |
| 20856 | 1067 |
| 22328 | 1068 Examples: |
| 1069 - Drop `:call` for calling a function and `:eval` for manipulating data. | |
| 1070 - Drop using a leading backslash for line continuation, automatically figure | |
| 1071 out where an expression ends. | |
| 20856 | 1072 |
| 22328 | 1073 However, this does require that some things need to change: |
| 1074 - Comments start with # instead of ", to avoid confusing them with strings. | |
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1075 This is good anyway, it is known from several popular languages. |
| 22328 | 1076 - Ex command ranges need to be prefixed with a colon, to avoid confusion with |
| 1077 expressions (single quote can be a string or a mark, "/" can be divide or a | |
| 1078 search command, etc.). | |
| 1079 | |
| 1080 Goal is to limit the differences. A good criteria is that when the old syntax | |
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1081 is accidentally used you are very likely to get an error message. |
| 20856 | 1082 |
| 1083 | |
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1084 Syntax and semantics from popular languages ~ |
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1085 |
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1086 Script writers have complained that the Vim script syntax is unexpectedly |
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1087 different from what they are used to. To reduce this complaint popular |
| 20856 | 1088 languages are used as an example. At the same time, we do not want to abandon |
| 1089 the well-known parts of legacy Vim script. | |
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1090 |
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1091 For many things TypeScript is followed. It's a recent language that is |
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1092 gaining popularity and has similarities with Vim script. It also has a |
| 22328 | 1093 mix of static typing (a variable always has a known value type) and dynamic |
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1094 typing (a variable can have different types, this changes at runtime). Since |
| 22328 | 1095 legacy Vim script is dynamically typed and a lot of existing functionality |
| 1096 (esp. builtin functions) depends on that, while static typing allows for much | |
| 1097 faster execution, we need to have this mix in Vim9 script. | |
| 1098 | |
| 22171 | 1099 There is no intention to completely match TypeScript syntax and semantics. We |
| 1100 just want to take those parts that we can use for Vim and we expect Vim users | |
| 22328 | 1101 will be happy with. TypeScript is a complex language with its own history, |
| 1102 advantages and disadvantages. To get an idea of the disadvantages read the | |
| 1103 book: "JavaScript: The Good Parts". Or find the article "TypeScript: the good | |
|
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1104 parts" and read the "Things to avoid" section. |
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1105 |
| 22328 | 1106 People familiar with other languages (Java, Python, etc.) will also find |
| 1107 things in TypeScript that they do not like or do not understand. We'll try to | |
| 1108 avoid those things. | |
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1109 |
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1110 Specific items from TypeScript we avoid: |
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1111 - Overloading "+", using it both for addition and string concatenation. This |
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1112 goes against legacy Vim script and often leads to mistakes. For that reason |
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1113 we will keep using ".." for string concatenation. Lua also uses ".." this |
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1114 way. And it allows for conversion to string for more values. |
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1115 - TypeScript can use an expression like "99 || 'yes'" in a condition, but |
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1116 cannot assign the value to a boolean. That is inconsistent and can be |
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1117 annoying. Vim recognizes an expression with && or || and allows using the |
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1118 result as a bool. TODO: to be reconsidered |
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1119 - TypeScript considers an empty string as Falsy, but an empty list or dict as |
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1120 Truthy. That is inconsistent. In Vim an empty list and dict are also |
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1121 Falsy. |
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1122 - TypeScript has various "Readonly" types, which have limited usefulness, |
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1123 since a type cast can remove the immutable nature. Vim locks the value, |
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1124 which is more flexible, but is only checked at runtime. |
| 22171 | 1125 |
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1126 |
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1127 Declarations ~ |
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1128 |
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1129 Legacy Vim script uses `:let` for every assignment, while in Vim9 declarations |
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1130 are used. That is different, thus it's good to use a different command: |
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1131 `:var`. This is used in many languages. The semantics might be slightly |
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1132 different, but it's easily recognized as a declaration. |
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1133 |
| 23047 | 1134 Using `:const` for constants is common, but the semantics varies. Some |
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1135 languages only make the variable immutable, others also make the value |
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1136 immutable. Since "final" is well known from Java for only making the variable |
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1137 immutable we decided to use that. And then `:const` can be used for making |
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1138 both immutable. This was also used in legacy Vim script and the meaning is |
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1139 almost the same. |
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1140 |
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1141 What we end up with is very similar to Dart: > |
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1142 :var name # mutable variable and value |
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1143 :final name # immutable variable, mutable value |
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1144 :const name # immutable variable and value |
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1145 |
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1146 Since legacy and Vim9 script will be mixed and global variables will be |
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1147 shared, optional type checking is desirable. Also, type inference will avoid |
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1148 the need for specifying the type in many cases. The TypeScript syntax fits |
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1149 best for adding types to declarations: > |
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1150 var name: string # string type is specified |
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1151 ... |
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1152 name = 'John' |
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1153 const greeting = 'hello' # string type is inferred |
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1154 |
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1155 This is how we put types in a declaration: > |
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1156 var mylist: list<string> |
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1157 final mylist: list<string> = ['foo'] |
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1158 def Func(arg1: number, arg2: string): bool |
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1159 |
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1160 Two alternatives were considered: |
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1161 1. Put the type before the name, like Dart: > |
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1162 var list<string> mylist |
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1163 final list<string> mylist = ['foo'] |
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1164 def Func(number arg1, string arg2) bool |
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1165 2. Put the type after the variable name, but do not use a colon, like Go: > |
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1166 var mylist list<string> |
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1167 final mylist list<string> = ['foo'] |
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1168 def Func(arg1 number, arg2 string) bool |
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1169 |
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1170 The first is more familiar for anyone used to C or Java. The second one |
| 22565 | 1171 doesn't really have an advantage over the first, so let's discard the second. |
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1172 |
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1173 Since we use type inference the type can be left out when it can be inferred |
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1174 from the value. This means that after `var` we don't know if a type or a name |
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1175 follows. That makes parsing harder, not only for Vim but also for humans. |
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1176 Also, it will not be allowed to use a variable name that could be a type name, |
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1177 using `var string string` is too confusing. |
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1178 |
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1179 The chosen syntax, using a colon to separate the name from the type, adds |
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1180 punctuation, but it actually makes it easier to recognize the parts of a |
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1181 declaration. |
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1182 |
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1183 |
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1184 Expressions ~ |
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1185 |
| 22565 | 1186 Expression evaluation was already close to what other languages are doing. |
| 1187 Some details are unexpected and can be improved. For example a boolean | |
| 1188 condition would accept a string, convert it to a number and check if the | |
| 1189 number is non-zero. This is unexpected and often leads to mistakes, since | |
| 1190 text not starting with a number would be converted to zero, which is | |
| 22723 | 1191 considered false. Thus using a string for a condition would often not give an |
| 1192 error and be considered false. That is confusing. | |
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1193 |
| 23047 | 1194 In Vim9 type checking is stricter to avoid mistakes. Where a condition is |
| 22565 | 1195 used, e.g. with the `:if` command and the `||` operator, only boolean-like |
| 1196 values are accepted: | |
| 1197 true: `true`, `v:true`, `1`, `0 < 9` | |
| 1198 false: `false`, `v:false`, `0`, `0 > 9` | |
| 1199 Note that the number zero is false and the number one is true. This is more | |
| 22723 | 1200 permissive than most other languages. It was done because many builtin |
| 22565 | 1201 functions return these values. |
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1202 |
| 22565 | 1203 If you have any type of value and want to use it as a boolean, use the `!!` |
| 1204 operator: | |
| 1205 true: !`!'text'`, `!![99]`, `!!{'x': 1}`, `!!99` | |
| 1206 false: `!!''`, `!![]`, `!!{}` | |
| 1207 | |
| 1208 From a language like JavaScript we have this handy construct: > | |
| 1209 GetName() || 'unknown' | |
| 1210 However, this conflicts with only allowing a boolean for a condition. | |
| 1211 Therefore the "??" operator was added: > | |
| 1212 GetName() ?? 'unknown' | |
| 1213 Here you can explicitly express your intention to use the value as-is and not | |
| 1214 result in a boolean. This is called the |falsy-operator|. | |
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1215 |
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1216 |
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1217 Import and Export ~ |
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1218 |
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1219 A problem of legacy Vim script is that by default all functions and variables |
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1220 are global. It is possible to make them script-local, but then they are not |
| 22171 | 1221 available in other scripts. This defies the concept of a package that only |
| 1222 exports selected items and keeps the rest local. | |
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1223 |
| 21825 | 1224 In Vim9 script a mechanism very similar to the JavaScript import and export |
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1225 mechanism is supported. It is a variant to the existing `:source` command |
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1226 that works like one would expect: |
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1227 - Instead of making everything global by default, everything is script-local, |
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1228 unless exported. |
| 22171 | 1229 - When importing a script the symbols that are imported are explicitly listed, |
| 1230 avoiding name conflicts and failures if functionality is added later. | |
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1231 - The mechanism allows for writing a big, long script with a very clear API: |
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1232 the exported function(s) and class(es). |
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1233 - By using relative paths loading can be much faster for an import inside of a |
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1234 package, no need to search many directories. |
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1235 - Once an import has been used, it can be cached and loading it again can be |
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1236 avoided. |
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1237 - The Vim-specific use of "s:" to make things script-local can be dropped. |
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1238 |
| 20856 | 1239 When sourcing a Vim9 script from a legacy script, only the items defined |
| 1240 globally can be used, not the exported items. Alternatives considered: | |
| 1241 - All the exported items become available as script-local items. This makes | |
| 22171 | 1242 it uncontrollable what items get defined and likely soon leads to trouble. |
| 20856 | 1243 - Use the exported items and make them global. Disadvantage is that it's then |
| 1244 not possible to avoid name clashes in the global namespace. | |
| 1245 - Completely disallow sourcing a Vim9 script, require using `:import`. That | |
| 1246 makes it difficult to use scripts for testing, or sourcing them from the | |
| 1247 command line to try them out. | |
| 22171 | 1248 Note that you can also use `:import` in legacy Vim script, see above. |
| 20856 | 1249 |
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1250 |
| 22328 | 1251 Compiling functions early ~ |
| 1252 | |
| 1253 Functions are compiled when called or when `:defcompile` is used. Why not | |
| 1254 compile them early, so that syntax and type errors are reported early? | |
| 1255 | |
| 1256 The functions can't be compiled right away when encountered, because there may | |
| 1257 be forward references to functions defined later. Consider defining functions | |
| 1258 A, B and C, where A calls B, B calls C, and C calls A again. It's impossible | |
| 1259 to reorder the functions to avoid forward references. | |
| 1260 | |
| 1261 An alternative would be to first scan through the file to locate items and | |
| 1262 figure out their type, so that forward references are found, and only then | |
| 1263 execute the script and compile the functions. This means the script has to be | |
| 1264 parsed twice, which is slower, and some conditions at the script level, such | |
| 1265 as checking if a feature is supported, are hard to use. An attempt was made | |
| 1266 to see if it works, but it turned out to be impossible to make work nicely. | |
| 1267 | |
| 1268 It would be possible to compile all the functions at the end of the script. | |
| 1269 The drawback is that if a function never gets called, the overhead of | |
| 1270 compiling it counts anyway. Since startup speed is very important, in most | |
| 1271 cases it's better to do it later and accept that syntax and type errors are | |
| 1272 only reported then. In case these errors should be found early, e.g. when | |
| 1273 testing, the `:defcompile` command will help out. | |
| 1274 | |
| 1275 | |
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1276 Why not use an embedded language? ~ |
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1277 |
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1278 Vim supports interfaces to Perl, Python, Lua, Tcl and a few others. But |
| 22328 | 1279 these interfaces have never become widely used, for various reasons. When |
| 1280 Vim9 was designed a decision was made to make these interfaces lower priority | |
| 1281 and concentrate on Vim script. | |
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1282 |
| 22328 | 1283 Still, plugin writers may find other languages more familiar, want to use |
| 1284 existing libraries or see a performance benefit. We encourage plugin authors | |
| 1285 to write code in any language and run it as an external tool, using jobs and | |
| 1286 channels. We can try to make this easier somehow. | |
| 1287 | |
| 1288 Using an external tool also has disadvantages. An alternative is to convert | |
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1289 the tool into Vim script. For that to be possible without too much |
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1290 translation, and keeping the code fast at the same time, the constructs of the |
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1291 tool need to be supported. Since most languages support classes the lack of |
| 22171 | 1292 support for classes in Vim is then a problem. |
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1293 |
| 22328 | 1294 |
| 1295 Classes ~ | |
| 1296 | |
| 1297 Vim supports a kind-of object oriented programming by adding methods to a | |
| 1298 dictionary. With some care this can be made to work, but it does not look | |
| 1299 like real classes. On top of that, it's quite slow, because of the use of | |
| 1300 dictionaries. | |
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1301 |
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1302 The support of classes in Vim9 script is a "minimal common functionality" of |
| 22171 | 1303 class support in most languages. It works much like Java, which is the most |
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1304 popular programming language. |
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1305 |
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1306 |
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1307 |
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1308 vim:tw=78:ts=8:noet:ft=help:norl: |