# File lib/sass/script/functions.rb, line 764
    def hsla(hue, saturation, lightness, alpha)
      if calc?(hue) || calc?(saturation) || calc?(lightness) || calc?(alpha)
        return unquoted_string("hsla(#{hue}, #{saturation}, #{lightness}, #{alpha})")
      end
      assert_type hue, :Number, :hue
      assert_type saturation, :Number, :saturation
      assert_type lightness, :Number, :lightness
      assert_type alpha, :Number, :alpha
      check_alpha_unit alpha, 'hsla'

      h = hue.value
      s = saturation.value
      l = lightness.value

      # Don't store the string representation for function-created colors, both
      # because it's not very useful and because some functions aren't supported
      # on older browsers.
      Sass::Script::Value::Color.new(
        :hue => h, :saturation => s, :lightness => l, :alpha => alpha.value)
    end