Created
March 29, 2011 13:28
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naive currying in javascript and php (yes! really!)
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// this is a helper for the curry function which does partial | |
// function application; given the function fn, an optional scope | |
// self and a variable number of arguments this function returns | |
// a new function which is bound to self with all arguments applied. | |
// example: | |
// function add(a, b) { | |
// return a + b; | |
// } | |
// var inc = partial(add, null, 1); | |
// assert(inc(4) == 5); | |
function partial(fn, self) { | |
var parr = Array.prototype; | |
var args = parr.slice.call(arguments, 2); | |
return function() { | |
return fn.apply(self, args.concat(parr.slice.call(arguments))); | |
}; | |
} | |
// this function applies currying to the given function, that means, that | |
// a new function is returned which if called with too few arguments | |
// returns a partially applied function. | |
// example: | |
// curry(function(z,y,x) { | |
// return [x,y,z]; | |
// }); | |
// var vec2 = vec3(0); | |
// var vec1 = vec2(0); | |
// assert(vec1(1) == [1,0,0]) | |
// assert(vec2(1,2) == [1,2,0]) | |
function curry(fn, self) { | |
return function() { | |
if (arguments.length < fn.arity) { | |
var args = [fn, self]; | |
args = args.concat(Array.prototype.slice.call(arguments)); | |
var p = partial.apply(null, args); | |
p.arity = fn.arity - arguments.length; | |
return curry(p, self); | |
} | |
else { | |
return fn.apply(self, arguments); | |
} | |
}; | |
} |
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<?php | |
/** | |
* partial function application | |
* | |
* @params callable $fn the function you want to apply partially | |
* | |
* example: | |
* function add($a, $b) { | |
* return $a + $b; | |
* } | |
* $inc = partial('add', 1); | |
* assert($inc(1) == 2); | |
*/ | |
function partial() { | |
$args = func_get_args(); | |
$fn = array_shift($args); | |
return function() use ($fn, $args) { | |
$myargs = func_get_args(); | |
return call_user_func_array($fn, array_merge($args, $myargs)); | |
}; | |
} | |
/** | |
* function currying | |
* | |
* @param callable $fn the function to curry | |
* | |
* example: | |
* $vec3 = curry(function($z, $y, $x) { | |
* return array($x, $y, $z); | |
* }); | |
* $vec2 = $vec3(0); | |
* assert($vec2(1,2) == array(2,1,0)); | |
* $vec1 = $vec2(7); | |
* assert($vec1(3) == array(3,7,0)); | |
*/ | |
function curry($fn, $arity = null) { | |
$ref = new ReflectionFunction($fn); | |
if ($arity == null) { | |
$arity = $ref->getNumberOfRequiredParameters(); | |
} | |
return function() use ($arity, $fn) { | |
$numArgs = func_num_args(); | |
if ($numArgs < $arity) { | |
$args = func_get_args(); | |
array_unshift($args, $fn); | |
$p = call_user_func_array('partial', $args); | |
$newArity = $arity - $numArgs; | |
return curry($p, $newArity); | |
} | |
else { | |
return call_user_func_array($fn, func_get_args()); | |
} | |
}; | |
} |
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