class Sass::Script::Number

def operate(other, operation)
  this = self
  if [:+, :-, :<=, :<, :>, :>=].include?(operation)
    if unitless?
      this = this.coerce(other.numerator_units, other.denominator_units)
    else
      other = other.coerce(numerator_units, denominator_units)
    end
  end
  # avoid integer division
  value = (:/ == operation) ? this.value.to_f : this.value
  result = value.send(operation, other.value)
  if result.is_a?(Numeric)
    Number.new(result, *compute_units(this, other, operation))
  else # Boolean op
    Bool.new(result)
  end
end