Show how to optimize corecursive functions using …exceptions?!

evenness.js

var throwup = require('throw').throwup, makecallable = require('throw').makecallable;

var even = throwup(_even), 
    odd = throwup(_odd);

var r = makecallable(_even)(parseInt(process.argv[2], 10) || 5000, 0);
console.log('found2', r);

function _even(n,j) {
    if(n>0) return odd(n-1, j+1);
    else return ['even', j];
}
function _odd(n, j) {
    if(n>0) return even(n-1, j+1);
    else return ['odd', j];
}