40 lines
1.7 KiB
Markdown
40 lines
1.7 KiB
Markdown
---
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tags: api/lua
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references:
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- client/space_lua/stdlib/string.ts
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- client/space_lua/stdlib/string_pack.ts
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---
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The `string` module contains Lua string operations and Space Lua extensions.
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> **note** Note
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> Since string values use `string` as their metatable, these APIs can also be called as methods. For example, `someString:startsWith("h")` is equivalent to `string.startsWith(someString, "h")`.
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## Lua pattern matching
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Lua patterns are not regular expressions. Space Lua translates Lua patterns to JavaScript regular expressions and has a few compatibility differences:
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1. Magic characters `^$()%.[]*+-?` must be escaped to represent literal characters. Standard Lua does not require escaping a magic character when it is not contextually magic, so patterns such as `%d--` can behave differently in Space Lua.
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2. Space Lua allows repetition characters (`?`, `*`, `+`, and `-`) to apply to captures; standard Lua does not.
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3. The *n*th captured string (`%n`), balanced match (`%bxy`), and frontier pattern (`%f[set]`) forms from the [Lua 5.4 pattern manual](https://www.lua.org/manual/5.4/manual.html#6.4.1) may not be supported.
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The `string.matchRegex` and `string.matchRegexAll` extensions use JavaScript regular expressions instead of Lua patterns.
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Examples of patterns that differ:
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```lua
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print(string.match("1234", "(%d)+"))
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-- Space Lua prints "4" because repetition applies to the capture.
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-- Standard Lua returns nil.
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print(string.match("*", "*"))
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-- Space Lua reports an invalid regular expression.
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-- Standard Lua prints "*".
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print(string.match("2024-03-14", "%d+-(%d+)-%d+"))
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-- Space Lua reports an invalid regular expression because the hyphens are not escaped.
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-- Standard Lua prints "03".
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```
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${spacelua.renderApiDocumentation("string")}
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