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Lua 5.1 lexical patterns
Version: 0.1.2
Generated: November 26, 2007

# Description

This module exports several Lua lexical patterns, all implemented in LPeg. None of them have captures.

# Dependencies

- LPeg

# Example

The following example lists all the tokens in a Lua script:

    local lpeg = require 'lpeg'
    local scanner = require 'leg.scanner'

     -- this pattern captures all tokens, ignores spaces and comments,
     -- and matches with end of file, giving an error otherwise
    patt = (lpeg.C(scanner.TOKEN) + scanner.SPACE + scanner.COMMENT)^0
        * (scanner.EOF + scanner.error'invalid character')
    patt = lpeg.Ct(patt)

     -- opens the file passed as parameter and tries to match with patt
    f = assert(io.open(arg[1]))

     -- a table storing all the tokens
    ALL = patt:match(f:read'*a')
    f:close()

     -- dumps all tokens on screen
    for _, tk in ipairs(ALL) do
       print(tk)
    end

# Variables

    ANY = LPeg pattern
| Matches any token, comment or space.
    BANG = LPeg pattern
| Matches UNIX's shebang (e.g. `#!/usr/bin/lua`).
    BOF = LPeg pattern
| Matches the beginning of a file.
    COMMENT = LPeg pattern
| Matches any type of comment.
    EOF = LPeg pattern
| Matches the end of a file.
    IDENTIFIER = LPeg pattern
| Matches any Lua identifier.
    IGNORED = LPeg pattern
| Matches everything ignored by the parser.
    KEYWORD = LPeg pattern
| A pattern which matches any Lua keyword.
    keywords = {}
| A table with Lua keyword-matching patterns, with the keywords in uppercase as keys. Examples: `keywords.WHILE`, `keywords['ELSEIF']`.
    NUMBER = LPeg pattern
| Matches any Lua number.
    SPACE = LPeg pattern
| Matches any space character.
    STRING = LPeg pattern
| Matches any Lua string.
    SYMBOL = LPeg pattern
| A pattern which matches any Lua symbol.
    symbols = {}
| A table with Lua symbol-matching patterns, with the symbols themselves as keys. Examples: `symbols['{']`, `symbols['+']`.
    TOKEN = LPeg pattern
| Matches any Lua identifier, keyword, symbol, number or string.

# Functions

`comment2text (comment)` | Strips all prefixing `--` and enclosing `--[=*[` from comment tokens.
`error (msg)` | Returns a function which throws lexical errors.
`string2text (str)` | Strips all enclosing `'`, `"`, and `[=*[` from string tokens, and processes escape characters.
`text2comment (text)` | Encloses the text with comment markers.
`text2string (text)` | Transforms a text into a syntactically valid Lua string. Similar to `string.format` with the `'%q'` option, but inserting escape numbers and escape codes where applicable.

`comment2text (comment)`

Strips all prefixing `--` and enclosing `--[=*[` from comment tokens.

Parameters:

- `comment`: the comment to strip.

Returns:

- the text without comment marking syntax.

`error (msg)`

Returns a function which throws lexical errors.

Parameters:

- `msg`: the message to be concatenated to the error message.

Returns:

- A function built to be used as a LPeg pattern, which will throw an error when matched.

Usage example:

    patt = intended_pattern^0 * (EOF + error'character after EOF')

It may also be used as a normal function:

    function (subject, i)
     if bad_condition then
       error'bad condition'(subject, i)
     end
    end

`string2text (str)`

Strips all enclosing `'`, `"`, and `[=*[` from string tokens, and processes escape characters.

Parameters:

- `str`: the string to strip.

Returns:

- the text without string enclosers.

`text2comment (text)`

Encloses the text with comment markers.

Parameters:

- `text`: the text to comment.

Returns:

- the text with comment marking syntax.

`text2string (text)`

Transforms a text into a syntactically valid Lua string. Similar to `string.format` with the `'%q'` option, but inserting escape numbers and escape codes where applicable.

Parameters

- `text`: a string containing the text.

Returns:

- a string, similar to string.format with option `'%q'`.