Data commit

Task/Church-numerals/PHP/church-numerals.php

@@ -0,0 +1,56 @@
+<?php
+$zero = function($f) { return function ($x) { return $x; }; };
+
+$succ = function($n) {
+  return function($f) use (&$n) {
+    return function($x) use (&$n, &$f) {
+      return $f( ($n($f))($x) );
+    };
+  };
+};
+
+$add = function($n, $m) {
+  return function($f) use (&$n, &$m) {
+    return function($x) use (&$f, &$n, &$m) {
+      return ($m($f))(($n($f))($x));
+    };
+  };
+};
+
+$mult = function($n, $m) {
+  return function($f) use (&$n, &$m) {
+    return function($x) use (&$f, &$n, &$m) {
+      return ($m($n($f)))($x);
+    };
+  };
+};
+
+$power = function($b,$e) {
+  return $e($b);
+};
+
+$to_int = function($f) {
+  $count_up = function($i) { return $i+1; };
+  return ($f($count_up))(0);
+};
+
+$from_int = function($x) {
+  $countdown = function($i) use (&$countdown) {
+    global $zero, $succ;
+    if ( $i == 0 ) {
+      return $zero;
+    } else {
+      return $succ($countdown($i-1));
+    };
+  };
+  return $countdown($x);
+};
+
+$three = $succ($succ($succ($zero)));
+$four = $from_int(4);
+foreach (array($add($three,$four), $mult($three,$four),
+	       $power($three,$four), $power($four,$three)) as $ch) {
+  print($to_int($ch));
+  print("\n");
+}
+?>