Contents

module Veritas
  module Logic
    class Connective

      # A logical negation of an expression
      class Negation < Unary

        # Evaluate the operands using a logical NOT
        #
        # @example with true operand
        #   Negation.call(true)  # => false
        #
        # @example with false operand
        #   Negation.call(false)  # => true
        #
        # @param [Boolean] operand
        #
        # @return [Boolean]
        #
        # @api public
        def self.call(operand)
          !operand
        end

        # Return the operand
        #
        # @example
        #   operand = negation.inverse
        #
        # @return [Expression]
        #
        # @api public
        def inverse
          operand
        end

        # Return a string representing the negation
        #
        # @example
        #   negation.inspect  # not(<Expression>)
        #
        # @return [String]
        #
        # @api public
        def inspect
          "not(#{operand.inspect})"
        end

        module Methods
          extend Aliasable

          # alias #! to #inverse when available
          inheritable_alias('!' => :inverse) if Object.method_defined?('!')

          inheritable_alias(:- => :not)

          # Logically negate then AND the expression
          #
          # @example
          #   conjunction = expression.not(other)
          #
          # @param [Expression] other
          #
          # @return [Conjunction]
          #
          # @api public
          def not(other)
            self.and(Negation.new(other))
          end

        end # module Methods

        Expression.class_eval { include Methods }

      end # class Negation
    end # class Connective
  end # module Logic
end # module Veritas

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
veritas-0.0.3	lib/veritas/logic/connective/negation.rb
veritas-0.0.2	lib/veritas/logic/connective/negation.rb
veritas-0.0.1	lib/veritas/logic/connective/negation.rb