Curried Javascript Functions

http://javascript.crockford.com/www_svendtofte_com/code/curried_javascript/index.html

by ccarpenterg • 17 years ago

30 10 17 years ago

javascript.crockford.com

troels• 17 years ago

Oldie but goodie. If you liked that, you might like this too: [Higher Order Programming in Javascript](http://w3future.com/html/stories/hop.xml)

apu• 17 years ago

If you already know all about higher-order programming and just want a javascript library with all the haskell/ML-style goodness, I highly recommend O. Steele's Functional library: http://osteele.com/sources/javascript/functional/

If nothing else, then his lambda() implementation with strings should be enough to convince you to use it.

ilyak• 17 years ago

Prototype has curry() and bind() methods on functions for some time.

http://prototypejs.org/api/function

String.prototype.splitOnSpaces = String.prototype.split.curry(" "); "foo bar baz thud".splitOnSpaces(); //-> ["foo", "bar", "baz", "thud"]

lhorie• 17 years ago

This:

  "foo bar baz thud".splitOnSpaces(); //-> ["foo", "bar", "baz", "thud"]

can be written like this:

  $w("foo bar baz thud")

jganetsk2• 17 years ago

Here's an implementation that I think is shorter, simpler to understand, easier to use, and doesn't require modifying existing functions for currification

  function curry(fn) {
    var wrappedFnMaker = function(accArgs) {
        return function() {
            var effectiveArgs = accArgs.concat(Array.prototype.slice.call(arguments));
            if (effectiveArgs.length >= fn.length) {
                return fn.apply(this, effectiveArgs);
            } else {
                return wrappedFnMaker(effectiveArgs);
            }
        };
    }
    return wrappedFnMaker([]);
  }

  add = curry(function(a,b,c) { return a + b + c; });

marcmarc• 17 years ago

Here's my take:

  function curry(fn, args) {
    if (typeof args == "undefined" || args.length < fn.length)
      return function() {
	if (typeof args == "undefined")
	  args = [];
	return curry(fn, args.concat(Array.prototype.slice.call(arguments)));
      };
    return fn.apply(this, args);
  }
  var add = curry(function(a, b, c) { return a + b + c;});

jganetsk2• 17 years ago

Both of our implementations have broken this. Damn you, Javascript this.

In principle, these two lines of code should always produce the same result:

  foo.bar(1,2)

and

  foo.bar(1)(2)

And they won't necessarily in our case, if the function uses this.

shaunxcode• 17 years ago

Here is curry in php 5.3

  function curry(){
    $args = func_get_args();
    $fn = array_shift($args);
    return function() use(&$fn, &$args) {
        $nargs = func_get_args();
        foreach($nargs as $narg) $args[] = $narg;
        return call_user_func_array($fn, $args);
    };
  }

  $add20 = curry(function($a, $b){return $a + $b;}, 20);

  echo $add20(5); #25

bodhi• 17 years ago

What's the deal with the stuff in the footer of this page? "The original page disappeared a couple of years ago. This is an unauthorized copy." It links to http://www.svendtofte.com/code/curried_javascript/ which I guess is the original article?

axod• 17 years ago

Currying looks horrible IMHO. It's like goto but worse. Can anyone give a real life example of why it's useful or desired?

Curried Javascript Functions

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