PHP でカリー化

2014-10-10 23:50 追記

GitHub および Packagist に公開しました。
https://github.com/yuya-takeyama/curry
https://packagist.org/packages/yuyat/curry

---

眠いのでコードのメモだけ。

<?php
class CurryingFunction
{
    private $fn;

    private $count;

    private $args;

    public function __construct($fn, $count, $args)
    {
        $this->fn = $fn;
        $this->count = $count;
        $this->args = $args;
    }

    public function apply($x)
    {
        $count = $this->count;
        $nextArgs = $this->args;

        foreach (func_get_args() as $arg) {
            $nextArgs[] = $arg;
            $count -= 1;

            if ($count < 1) {
                break;
            }
        }

        if ($count < 1) {
            return call_user_func_array($this->fn, $nextArgs);
        } else {
            return new static($this->fn, $count, $nextArgs);
        }
    }

    public function __invoke($x)
    {
        return call_user_func_array(array($this, 'apply'), func_get_args());
    }
}

function curry($fn, $count = null) {
    if (!$count) {
        $ref = new ReflectionFunction($fn);
        $count = $ref->getNumberOfParameters();
    }

    return new CurryingFunction($fn, $count, array());
}

$f = curry(function ($x, $y, $z) { return $x + $y + $z; });

var_dump($f(1)->apply(2)->apply(3));
// => 6
var_dump($f(1, 2)->apply(3));
// => 6
var_dump($f(1, 2, 3));
// => 6