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# Load the builder class
require_relative '../../../lib/rley/syntax/grammar_builder'
require_relative '../../../lib/rley/parser/token'
module GrammarAmbig01Helper
########################################
# Factory method. Define a grammar for a very simple language
# Grammar 3: An ambiguous arithmetic expression language
# (based on example in article on Earley's algorithm in Wikipedia)
def grammar_ambig01_builder()
builder = Rley::Syntax::GrammarBuilder.new
builder.add_terminals('integer', '+', '*')
builder.add_production('P' => 'S')
builder.add_production('S' => %w(S + S))
builder.add_production('S' => %w(S * S))
builder.add_production('S' => 'L')
builder.add_production('L' => 'integer')
builder
end
# Highly simplified tokenizer implementation.
def tokenizer_ambig01(aText, aGrammar)
tokens = aText.scan(/\S+/).map do |lexeme|
case lexeme
when '+', '*'
terminal = aGrammar.name2symbol[lexeme]
when /^[-+]?\d+$/
terminal = aGrammar.name2symbol['integer']
else
msg = "Unknown input text '#{lexeme}'"
raise StandardError, msg
end
Rley::Parser::Token.new(lexeme, terminal)
end
return tokens
end
end # module
# End of file
Version data entries
6 entries across 6 versions & 1 rubygems