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-- ? LPeg lexer.
local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S
local lex = lexer.new('?')
-- Whitespace.
lex:add_rule('whitespace', token(lexer.WHITESPACE, lexer.space^1))
-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
keyword1 keyword2 keyword3
]]))
-- Identifiers.
lex:add_rule('identifier', token(lexer.IDENTIFIER, lexer.word))
-- Strings.
lex:add_rule('string', token(lexer.STRING, lexer.delimited_range("'") +
lexer.delimited_range('"')))
-- Comments.
lex:add_rule('comment', token(lexer.COMMENT, '#' * lexer.nonnewline^0))
-- Numbers.
lex:add_rule('number', token(lexer.NUMBER, lexer.float + lexer.integer))
-- Operators.
lex:add_rule('operator', token(lexer.OPERATOR, S('+-*/%^=<>,.{}[]()')))
-- Fold points.
lex:add_fold_point(lexer.KEYWORD, 'start', 'end')
lex:add_fold_point(lexer.OPERATOR, '{', '}')
lex:add_fold_point(lexer.COMMENT, '#', lexer.fold_line_comments('#'))
return lex
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