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require 'strscan'
# Load the builder class
require_relative '../../../lib/rley/syntax/grammar_builder'
require_relative '../../../lib/rley/lexical/token'
module GrammarArrIntHelper
# Factory method. Creates a grammar builder for a grammar of
# array of integers.
# (based on the article about Earley's algorithm in Wikipedia)
def grammar_arr_int_builder()
builder = Rley::Syntax::GrammarBuilder.new do
add_terminals('[', ']', ',', 'integer')
rule 'P' => 'arr'
rule 'arr' => %w([ sequence ])
rule 'sequence' => 'list'
rule 'sequence' => []
rule 'list' => %w[list , integer] # Left-recursive rule
rule 'list' => 'integer'
end
builder
end
# Basic tokenizer for array of integers
def arr_int_tokenizer(aText, aGrammar)
tokens = []
scanner = StringScanner.new(aText)
until scanner.eos?
scanner.skip(/\s+/)
lexeme = scanner.scan(/[\[,\]]/)
if lexeme
terminal = aGrammar.name2symbol[lexeme]
tokens << Rley::Lexical::Token.new(lexeme, terminal)
next
end
lexeme = scanner.scan(/^[-+]?\d+/)
if lexeme
terminal = aGrammar.name2symbol['integer']
tokens << Rley::Lexical::Token.new(lexeme, terminal)
else
msg = "Unknown input text '#{lexeme}'"
raise StandardError, msg
end
end
return tokens
end
end # module
# End of file
Version data entries
10 entries across 10 versions & 1 rubygems