require 'sass/constant/string'
require 'sass/constant/number'
require 'sass/constant/color'

module Sass::Constant
  class Operation
    def initialize(operand1, operand2, operator)
      @operand1 = operand1
      @operand2 = operand2
      @operator = operator
    end
    
    def to_s
      self.perform.to_s
    end
    
    protected
    
    def perform
      literal1 = @operand1.perform
      literal2 = @operand2.perform
      begin
        literal1.send(@operator, literal2)
      rescue NoMethodError => e
        raise e unless e.name == @operator
        raise Sass::SyntaxError.new("Undefined operation: \"#{literal1} #{@operator} #{literal2}\"")
      end
    end
  end
end