Beans_Lessc::reduce PHP Method

    protected function reduce($value, $forExpression = false)
    {
        switch ($value[0]) {
            case "interpolate":
                $reduced = $this->reduce($value[1]);
                $var = $this->compileValue($reduced);
                $res = $this->reduce(array("variable", $this->vPrefix . $var));
                if ($res[0] == "raw_color") {
                    $res = $this->coerceColor($res);
                }
                if (empty($value[2])) {
                    $res = $this->lib_unquote($res);
                }
                return $res;
            case "variable":
                $key = $value[1];
                if (is_array($key)) {
                    $key = $this->reduce($key);
                    $key = $this->vPrefix . $this->compileValue($this->lib_unquote($key));
                }
                $seen =& $this->env->seenNames;
                if (!empty($seen[$key])) {
                    $this->throwError("infinite loop detected: {$key}");
                }
                $seen[$key] = true;
                $out = $this->reduce($this->get($key, self::$defaultValue));
                $seen[$key] = false;
                return $out;
            case "list":
                foreach ($value[2] as &$item) {
                    $item = $this->reduce($item, $forExpression);
                }
                return $value;
            case "expression":
                return $this->evaluate($value);
            case "string":
                foreach ($value[2] as &$part) {
                    if (is_array($part)) {
                        $strip = $part[0] == "variable";
                        $part = $this->reduce($part);
                        if ($strip) {
                            $part = $this->lib_unquote($part);
                        }
                    }
                }
                return $value;
            case "escape":
                list(, $inner) = $value;
                return $this->lib_unquote($this->reduce($inner));
            case "function":
                $color = $this->funcToColor($value);
                if ($color) {
                    return $color;
                }
                list(, $name, $args) = $value;
                if ($name == "%") {
                    $name = "_sprintf";
                }
                $f = isset($this->libFunctions[$name]) ? $this->libFunctions[$name] : array($this, 'lib_' . $name);
                if (is_callable($f)) {
                    if ($args[0] == 'list') {
                        $args = self::compressList($args[2], $args[1]);
                    }
                    $ret = call_user_func($f, $this->reduce($args, true), $this);
                    if (is_null($ret)) {
                        return array("string", "", array($name, "(", $args, ")"));
                    }
                    // convert to a typed value if the result is a php primitive
                    if (is_numeric($ret)) {
                        $ret = array('number', $ret, "");
                    } elseif (!is_array($ret)) {
                        $ret = array('keyword', $ret);
                    }
                    return $ret;
                }
                // plain function, reduce args
                $value[2] = $this->reduce($value[2]);
                return $value;
            case "unary":
                list(, $op, $exp) = $value;
                $exp = $this->reduce($exp);
                if ($exp[0] == "number") {
                    switch ($op) {
                        case "+":
                            return $exp;
                        case "-":
                            $exp[1] *= -1;
                            return $exp;
                    }
                }
                return array("string", "", array($op, $exp));
        }
        if ($forExpression) {
            switch ($value[0]) {
                case "keyword":
                    if ($color = $this->coerceColor($value)) {
                        return $color;
                    }
                    break;
                case "raw_color":
                    return $this->coerceColor($value);
            }
        }
        return $value;
    }