Generator function tasks

test.js

var MiningTask = function* MiningTask() {
    for(var i=0; i<5; i++) {
        yield breakBlock();
    }
}

var tasks = [];

tasks.push(MiningTask());

var tick = function() {
    var task = tasks.pop();
    var r = task.next();
    if(!r.done)
        tasks.push(r);
    process.nextTick(tick);
};