var fibonacci = function (n) {
return n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2);
};

var memoizer = function (memo, fundamental) {
var shell = function (n) {
var result = memo[n];
if (typeof result !== 'number') {
result = fundamental(shell, n);
memo[n] = result;
}
return result;
};
return shell;
};

var fibonacci = memoizer([0, 1], function (shell, n) {
return shell(n - 1) + shell(n - 2);
});

var factorial = memoizer([1, 1], function (shell, n) {
return n * shell(n - 1);
});