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@i-am-tom
Last active October 1, 2016 22:34
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The Y (and U) combinator(s), with an example, implemented in PHP.
<?php
$fib = function ($f) {
return function ($n) use ($f) {
switch ($n) {
case 0: return 0;
case 1: return 1;
default:
return $f ($n - 1)
+ $f ($n - 2);
}
};
};
Y ($fib) (10);
<?php
function U ($f) {
return $f ($f);
}
function Y ($f) {
return U (function ($x) use ($f) {
return $f (function ($y) use ($x) {
return U ($x) ($y);
});
});
}
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