56 lines
1.5 KiB
Ruby
56 lines
1.5 KiB
Ruby
require "strscan"
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module Liquid
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class Lexer
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SPECIALS = {
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'|'.freeze => :pipe,
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'.'.freeze => :dot,
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':'.freeze => :colon,
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','.freeze => :comma,
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'['.freeze => :open_square,
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']'.freeze => :close_square,
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'('.freeze => :open_round,
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')'.freeze => :close_round,
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'?'.freeze => :question,
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'-'.freeze => :dash
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}.freeze
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IDENTIFIER = /[a-zA-Z_][\w-]*\??/
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SINGLE_STRING_LITERAL = /'[^\']*'/
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DOUBLE_STRING_LITERAL = /"[^\"]*"/
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NUMBER_LITERAL = /-?\d+(\.\d+)?/
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DOTDOT = /\.\./
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COMPARISON_OPERATOR = /==|!=|<>|<=?|>=?|contains(?=\s)/
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WHITESPACE_OR_NOTHING = /\s*/
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def initialize(input)
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@ss = StringScanner.new(input)
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end
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def tokenize
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@output = []
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until @ss.eos?
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@ss.skip(WHITESPACE_OR_NOTHING)
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break if @ss.eos?
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tok = case
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when t = @ss.scan(COMPARISON_OPERATOR) then [:comparison, t]
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when t = @ss.scan(SINGLE_STRING_LITERAL) then [:string, t]
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when t = @ss.scan(DOUBLE_STRING_LITERAL) then [:string, t]
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when t = @ss.scan(NUMBER_LITERAL) then [:number, t]
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when t = @ss.scan(IDENTIFIER) then [:id, t]
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when t = @ss.scan(DOTDOT) then [:dotdot, t]
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else
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c = @ss.getch
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if s = SPECIALS[c]
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[s, c]
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else
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raise SyntaxError, "Unexpected character #{c}"
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end
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end
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@output << tok
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end
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@output << [:end_of_string]
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end
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end
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end
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