Class: Panini::DerivationStrategy::Leftmost

Inherits:
Base
  • Object
show all
Defined in:
lib/derivation_strategy/leftmost.rb

Overview

The Leftmost strategy is a naive strategy for deriving sentences from a grammar. It will aways substitute for the leftmost nonterminal first. If a nonterminal has more than one production, they will be chosen in a round-robin ordering.

This implementation is slow and will not work on many grammars.

In other words, don’t use this! It’s in place because it is simple to and was used for early testing.

Instance Method Summary collapse

Constructor Details

#initialize(grammar) ⇒ Leftmost

Returns a new instance of Leftmost.



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# File 'lib/derivation_strategy/leftmost.rb', line 30

def initialize(grammar)
  build_production_proxies(grammar)
  super(grammar)
end

Instance Method Details

#sentence ⇒ Object

Generates a sentence.



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# File 'lib/derivation_strategy/leftmost.rb', line 44

def sentence
  derived_sentence, substituted = [@grammar.start], false
  begin
    derived_sentence, substituted = substitution_pass(derived_sentence)
  end while substituted
  derived_sentence
end