Javascripts

memoizer.js

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

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

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