jkr2255 / prop_logic

module PropLogic

  class Variable < Term

    def initialize(name = nil)

      @name = name || "v_#{object_id}"

      @terms = [].freeze

      freeze

    end

    public_class_method :new

    def to_s(*)

      @name

    end

    def nnf?

      true

    end

    def reduced?

      true

    end

    def to_cnf

      self

    end

    def tseitin(pool)

      self

    end

    def cnf?

      true

    end

    def variables

      [self]

    end

    def assign(trues, falses, variables = nil)

      if trues.include? self

        True

      elsif falses.include? self

        False

      else

        self

      end

    end

    # bypassing Term.get

    # @return [NotTerm] negated variable

    def not

      Term.__send__ :cached, NotTerm, self

    end

    alias_method :~, :not

    alias_method :-@, :not