class Dentaku::AST::Arithmetic

def initialize(*)
  super
  unless valid_left?
    raise NodeError.new(:numeric, left.type, :left),
          "#{self.class} requires numeric operands"
  end
  unless valid_right?
    raise NodeError.new(:numeric, right.type, :right),
          "#{self.class} requires numeric operands"
  end
end