gistfile1.js

Function.prototype.cache = function(){
  var _cache = {};

  var key = function(args) {
    var sig = 'x', index = args.length;
    while (index--) {
      sig += args[index].toString();
    }
    return sig;
  }

  this.store = function(args, v){
    _cache[key(args)] = v;
    return v;
  }

  this.fetch = function(args) {
    var k = key(args);
    if (k in _cache) {
      return _cache[k];
    } else {
      return null;
    }
  }

  return this;
}();


function sum() {
  if (sum.cache.fetch(arguments) != null) {
    return sum.cache.fetch(arguments);
  }

  var total = 0, length = arguments.length;
  while (length--) {
    total += arguments[length];
  }
  return sum.cache.store(arguments, total)
}


function sin(num) {
  if (sin.cache.fetch(arguments) != null) {
    return sin.cache.fetch(arguments);
  }
  var s = Math.sin(num)
  return sin.cache.store(arguments, s)
}