Trampolining

trampoline1.js

// with recursion:
var results = [1,1];
function recufib(N) {


    function getN() {
        var a = results[results.length-2]
        var b = results[results.length-1];        
        if(!--N) {
            return;
        } else {
            results.push(a+b);
            getN();
        }             
    };
    //return getN;
    getN();
}
recufib(30);
console.log(results) // cool

// using a trampoline!
var results=[1,1];
function fib(N) {


    function getN() {
        var a = results[results.length-2]
        var b = results[results.length-1];        
        if(!--N) {
            return;
        } else {
            results.push(a+b);
            return getN;
        }             
    };
    return getN;
}
b = fib(30);
while (b instanceof Function) {
    b = b(); // trampolining?
}

console.log(results)
/*
~/source/nodejs$ node tramp.js
[ 1,
  1,
  2,
  3,
  5,
  8,
  13,
  21,
  34,
  55,
  89,
  144,
  233,
  377,
  610,
  987,
  1597,
  2584,
  4181,
  6765,
  10946,
  17711,
  28657,
  46368,
  75025,
  121393,
  196418,
  317811,
  514229,
  832040,
  1346269 ]
*/