Showing possible semantics of transforming regular subroutines into coroutines.

coroutineExperiment2.js

// Original source code supplied by userland
function userFunc() {
	var one = 1;
	var two = 2;
	var three = one + two;
	return three;
}


// Same source code after compiling with HertzScript
const yieldSym = Symbol("HzYield");
function hzYield(value = yieldSym) {
	return {
		type: yieldSym,
		noValue: value === yieldSym,
		value: value
	};
}
const returnSym = Symbol("HzReturn");
function hzReturn(value = returnSym) {
	return {
		type: returnSym,
		noValue: value === returnSym,
		value: value
	}
}
function generatorFunc() {
	var hzLoc = 0;
	const state = {};
	function userFunc() {
		switch (hzLoc) {
			case 0:
			state.one = 1;
			hzLoc++;
			return hzYield();
			case 1:
			state.two = 2;
			hzLoc++;
			return hzYield();
			case 2:
			state.three = state.one + state.two;
			return hzReturn(state.three);
		}
		return hzReturn();
	}
	var done = false;
	return {
		next: function() {
			if (done) return {done: true, value: undefined};
			var hzValue = userFunc();
			if (hzValue.type === returnSym) done = true;
			return {
				done: done,
				value: hzValue.noValue ? undefined : hzValue.value
			};
		}
	};
}