Class: Calyx::Production::WeightedChoices

Inherits:
Object
  • Object
show all
Defined in:
lib/calyx/production/weighted_choices.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(collection) ⇒ WeightedChoices

Returns a new instance of WeightedChoices.



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# File 'lib/calyx/production/weighted_choices.rb', line 22

def initialize(collection)
  @collection = collection
end

Class Method Details

.parse(productions, registry) ⇒ Object 



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# File 'lib/calyx/production/weighted_choices.rb', line 4

def self.parse(productions, registry)
  weights_sum = productions.reduce(0) do |memo, choice|
    memo += choice.last
  end

  raise 'Weights must sum to 1' if weights_sum != 1.0

  choices = productions.map do |choice, weight|
    if choice.is_a?(String)
      [Concat.parse(choice, registry), weight]
    elsif choice.is_a?(Symbol)
      [NonTerminal.new(choice, registry), weight]
    end
  end

  self.new(choices)
end

Instance Method Details

#evaluate ⇒ Object 



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# File 'lib/calyx/production/weighted_choices.rb', line 26

def evaluate
  choice = @collection.max_by do |_, weight|
    rand ** (1.0 / weight)
  end.first

  [:weighted_choice, choice.evaluate]
end