hallettj · March 28, 2014 08:03
diff --git a/array_monad.js b/array_monad.js
 /*
 * The implementation
 */

 function du(comprehension) {
    return function(/* args */) {
        var gen = comprehension.apply(null, arguments)
        return next();

        function next(v) {
            var res = gen.next(v)
            return (!res.done && res.value) ? flatMap(res.value, tryNext) : res.value
        }

        function tryNext(v) {
            try {
                return next(v)
            }
            catch (err) {
                return gen.throw(err)
            }
        }
    }
 }

 function flatMap(m, f) {
    if (typeof m.then === 'function') {
        return m.then(f)
    }
    else if (typeof m.map === 'function' && typeof m.length === 'number') {
        return flatten(m.map(f))
    }
    else {
        throw new TypeError("No implementation for this argument!")
    }
 }

 function flatten(xs) {
    if (!xs || !xs.reduce) {
        return xs
    }
    return xs.reduce(function(flat, x) {
        return flat.concat(x)
    }, [])
 }


 /*
 * An array monad in action
 */

 var guests = [
    { name: "Sophia",    vegetarian: true,   peanutAllergy: false },
    { name: "Madison",   vegetarion: false,  peanutAllergy: false },
    { name: "Liam",      vegetarion: true,   peanutAllergy: true  },
    { name: "Noah",      vegetarian: true,   peanutAllergy: false },
    { name: "Elizabeth", vegetarian: false,  peanutAllergy: true  }
 ]

 var entrees = [
    { name: "Meatballs",    vegetarian: false, peanut: false },
    { name: "Pad Thai",     vegetarion: true,  peanut: true  },
    { name: "BLT",          vegetarion: false, peanut: false },
    { name: "Caesar Salad", vegetarian: true,  peanut: false },
    { name: "Game Hen",     vegetarian: false, peanut: true  }
 ]

 var acceptablePairings = du(function*() {
    var guest  = yield guests
    var entree = yield entrees
    if (guest.peanutAllergy && entree.peanut) {
        return []
    }
    else if (guest.vegetarian && !entree.vegetarian) {
        return []
    }
    else {
        return [[guest.name, entree.name]]
    }
 })();

 // Upon calling `gen.next()` with the second entree, an error is reported:
 //
 // > Error: Generator has already finished
	/*
	* The implementation
	*/

	function du(comprehension) {
	return function(/* args */) {
	var gen = comprehension.apply(null, arguments)
	return next();

	function next(v) {
	var res = gen.next(v)
	return (!res.done && res.value) ? flatMap(res.value, tryNext) : res.value
	}

	function tryNext(v) {
	try {
	return next(v)
	}
	catch (err) {
	return gen.throw(err)
	}
	}
	}
	}

	function flatMap(m, f) {
	if (typeof m.then === 'function') {
	return m.then(f)
	}
	else if (typeof m.map === 'function' && typeof m.length === 'number') {
	return flatten(m.map(f))
	}
	else {
	throw new TypeError("No implementation for this argument!")
	}
	}

	function flatten(xs) {
	if (!xs \|\| !xs.reduce) {
	return xs
	}
	return xs.reduce(function(flat, x) {
	return flat.concat(x)
	}, [])
	}


	/*
	* An array monad in action
	*/

	var guests = [
	{ name: "Sophia", vegetarian: true, peanutAllergy: false },
	{ name: "Madison", vegetarion: false, peanutAllergy: false },
	{ name: "Liam", vegetarion: true, peanutAllergy: true },
	{ name: "Noah", vegetarian: true, peanutAllergy: false },
	{ name: "Elizabeth", vegetarian: false, peanutAllergy: true }
	]

	var entrees = [
	{ name: "Meatballs", vegetarian: false, peanut: false },
	{ name: "Pad Thai", vegetarion: true, peanut: true },
	{ name: "BLT", vegetarion: false, peanut: false },
	{ name: "Caesar Salad", vegetarian: true, peanut: false },
	{ name: "Game Hen", vegetarian: false, peanut: true }
	]

	var acceptablePairings = du(function*() {
	var guest = yield guests
	var entree = yield entrees
	if (guest.peanutAllergy && entree.peanut) {
	return []
	}
	else if (guest.vegetarian && !entree.vegetarian) {
	return []
	}
	else {
	return [[guest.name, entree.name]]
	}
	})();

	// Upon calling `gen.next()` with the second entree, an error is reported:
	//
	// > Error: Generator has already finished
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