2009-12-08-162006.php

<?php

function fix($f) {
    return function($x) use ($f) {
        return $f(fix($f), $x);
    };
};

$map = function($f, $xs) {
    $func = fix(function($sf, $ys) use ($f) {
        if (count($ys) > 0) {
            $y = array_shift($ys);
            $a = $sf($ys);
            array_unshift($a, $f($y));
            return $a;
        } else {
            return array();
        }
    });
    return $func($xs);
};

$double = function($x) {return $x * 2;};
print_r($map($double, array(1,2,3)));

?>