Class: Panini::DerivationStrategy::RandomDampened

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

Overview

This derivation strategy uses a dampening factor to reduce the liklihood of hitting either too-deep or infinite traversals through the grammar. This is based on material presented here:

eli.thegreenplace.net/2010/01/28/generating-random-sentences-from-a-context-free-grammar

Instance Method Summary collapse

Constructor Details

#initialize(grammar, damping = 0.25) ⇒ RandomDampened

Initializes the derivator. The damping factor is a number betweeon 0.0 and 1.0. In general, the smaller the number the shorter the senetence generated by the derivator. If the number is close to 1.0, it is possible that you will encounter stack errors!



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# File 'lib/derivation_strategy/random_dampened.rb', line 69

def initialize(grammar, damping = 0.25)
  if (damping <= 0.0) || (damping >= 1.0)
    raise ArgumentError, "The damping factor must be greater than 0.0 and less than 1.0."
  end
  build_production_proxies(grammar, damping)
  super(grammar)
end

Instance Method Details

#sentence ⇒ Object

Generates a sentence.



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# File 'lib/derivation_strategy/random_dampened.rb', line 86

def sentence
  substitute_nonterminal(@grammar.start, @production_proxies, 0)
end