I assume you are referring to something like Q.async/Q.spawn to turn the generator into an async function using promises?
Sent from my Windows Phone ________________________________ From: Ron Buckton<mailto:[email protected]> Sent: 7/15/2013 5:02 PM To: Bruno Jouhier<mailto:[email protected]>; es-discuss<mailto:[email protected]> Subject: RE: generators vs forEach Bruno, wouldn't yield* work here to delegate the inner yields? Sent from my Windows Phone ________________________________ From: Bruno Jouhier<mailto:[email protected]> Sent: 7/15/2013 4:12 PM To: es-discuss<mailto:[email protected]> Subject: Re: generators vs forEach There is no need to CPS transform functions and there is no need for deferred functions either. It can all be done with today's generators and a little helper library. With the C# async/await notation: * The yield keyword is your "await" keyword. * The little * in function* is your "async" keyword. With this you can write: function* asyncEach(array, fn) { for (var i = 0; i < array.length; i++) yield fn(array[i], i); } and you can call it as: function* myFunc(array) { yield asyncEach(array, function*(elt, i) { var foo = yield asyncBar(elt); // more ... }) } Note that there is *no* helper API in all these async functions that call other async functions; The helper API is only needed to interface this with the classical callback world: at the very bottom of the stack when you call low level callbacks-based I/O functions, and at the top of the stack when the event loop runs one of your generator functions. The trick is that you need a clever run function to do the little yield/next dance with generator functions that call other generator functions. I've implemented this in https://github.com/bjouhier/galaxy/blob/master/lib/galaxy.js (the run and invoke functions) The only thing I don't like about it is the awkward syntax: * yield precedence does not work well * yield is prefix, which does not chain well * and yield is heavy anyway In short, this is a hack to get going but I'm still waiting for the full concurrency proposal and its awesome ! syntax. Bruno > Consider the following: > > function* yieldEach(array){ > array.forEach(n => { > yield n; > }); > } > > In order for this to work, not only does `yieldEach` have to be suspended for > the inner yield, but forEach does as well. That means CPS transforming > functions based on whether they call a yielding function.
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