51 lines
1.5 KiB
Ruby
51 lines
1.5 KiB
Ruby
module Imbecile
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class Grammar
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# @return [String, nil] Module name.
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attr_reader :modulename
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# @return [String, nil] Class name.
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attr_reader :classname
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def initialize(input_file)
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@tokens = {}
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@rules = {}
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File.read(input_file).each_line.each_with_index do |line, line_index|
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line = line.chomp
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line_number = line_index + 1
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if line =~ /^\s*#/
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# Skip comment lines.
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elsif line =~ /^\s*$/
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# Skip blank lines.
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elsif line =~ /^\s*module\s+(\S+)$/
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@modulename = $1
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elsif line =~ /^\s*class\s+(\S+)$/
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@classname = $1
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elsif line =~ /^\s*token\s+(\S+)(?:\s+(\S+))?$/
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name, pattern = $1, $2
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if pattern.to_s == ""
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pattern = name
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end
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unless name =~ /^[a-zA-Z_][a-zA-Z_0-9]*$/
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raise Error.new("Invalid token name #{name} on line #{line_number}")
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end
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if @tokens[name]
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raise Error.new("Duplicate token name #{name} on line #{line_number}")
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end
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@tokens[name] = {pattern: pattern}
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else
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raise Error.new("Unexpected input on line #{line_number}: #{line}")
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end
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end
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# Build NFA from each token expression.
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@tokens.each do |token_name, token_def|
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token_def[:regex] = Regex.new(token_def[:pattern])
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token_def[:regex].nfa.end_state.accepts = token_name
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end
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dfa = Regex::DFA.new(@tokens.map {|token_name, token_def| token_def[:regex].nfa})
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end
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end
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end
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