curry / schönfinkel example

curry.js

// http://blog.mgechev.com/2013/01/21/functional-programming-with-javascript/
/* By Stoyan Stafanov */
function schonfinkelize(fn) {
    var slice = Array.prototype.slice,
        stored_args = slice.call(arguments, 1);
    return function () {
        var new_args = slice.call(arguments),
            args = stored_args.concat(new_args);
        return fn.apply(null, args);
    };
}

// http://benalman.com/news/2012/09/partial-application-in-javascript/#currying
function curry(fn, n) {
  // If `n` argument was omitted, use the function .length property.
  if (typeof n !== 'number') {
    n = fn.length;
  }

  function getCurriedFn(prev) {
    return function(arg) {
      // Concat the just-specified argument with the array of
      // previously-specified arguments.
      var args = prev.concat(arg);
      if (args.length < n) {
        // Not all arguments have been satisfied yet, so return a curried
        // version of the original function.
        return getCurriedFn(args);
      } else {
        // Otherwise, invoke the original function with the arguments and
        // return its value.
        return fn.apply(this, args);
      }
    };
  }

  // Return a curried version of the original function.
  return getCurriedFn([]);
}

function someThing(a,b,c) {
    return (a + ", " + b + ", " + c);
}

function wait(count, callback){
    while(count > 0) {
        count--;
    }
    return callback;
}

console.time("procedure");

console.time("a");
var test = schonfinkelize(someThing, wait(10e4, "a"));
console.timeEnd("a");

console.time("b");
test = schonfinkelize(test, wait(10e6, "b"));
console.timeEnd("b");

console.time("c");
test("c");
console.timeEnd("c");

console.timeEnd("procedure");

console.log("-----");

console.time("procedure");

var testCurry = curry(someThing);
console.time("a");
var a = wait(10e4, "a");
console.timeEnd("a");

console.time("b");
var b = wait(10e6, "b");
console.timeEnd("b");

console.time("c");
var c = "c";
console.timeEnd("c");

console.time("currying");
console.log(testCurry(a)(b)(c));
console.timeEnd("currying");
console.timeEnd("procedure");


// ###### http://javascriptweblog.wordpress.com/2010/04/05/curry-cooking-up-tastier-functions/

Function.prototype.curry = function() {
    if (arguments.length<1) {
        return this; //nothing to curry with - return function
    }
    var __method = this,
        _toArrayFn = Array.prototype.slice,
        args = _toArrayFn.call(arguments);
    return function() {
        return __method.apply(this, args.concat(_toArrayFn.call(arguments)));
    }
}

var converter = function(ratio, symbol, input) {
    return [(input*ratio).toFixed(1),symbol].join(" ");
}
 
var kilosToPounds = converter.curry(2.2,"lbs");
var litersToUKPints = converter.curry(1.75, "imperial pints");
var litersToUSPints = converter.curry(1.98, "US pints");
var milesToKilometers = converter.curry(1.62, "km");
 
kilosToPounds(4); //8.8 lbs
litersToUKPints(2.4); //4.2 imperial pints
litersToUSPints(2.4); //4.8 US pints
milesToKilometers(34); //55.1 km

partial.js

var BC = {};
BC.partial = function (fn) {
    var slice = Array.prototype.slice, 
        args = slice.call(arguments, 1);
    return (function() {
        return fn.apply(this, args.concat(slice.call(arguments,0)));
    });
}

BC.add = function (a, b) {
    return a + b;
}

BC.increment = BC.partial(BC.add, 1);