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Comment by bayesianhorse | Hacker News Reader

Great idea. Generators are one of the features that still seperate coffeescript from python, in terms of productivity/elegance.

Still missing is a syntax to consume these generators, like in "for a in b" or "yield from"

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Definitely agree with need for iteration syntax and yieldfrom keyword. The iteration syntax will probably have be something different than "for a in b" because that's already used for array-like iteration and adding another case would slow existing code down (all of which wouldn't be using it of course). For yieldfrom the code it needs to generate is something like this:

    var generator = g1(), result = {}, send;
    while(!result.done) {
        result = generator.send(send);
        send = yield result.value;
    }

I would suggest "for a from b". If that only uses .next and .send, it might work with class instances too, like the iterator protocol in Python.

Good idea, I'll see if I can add that.

I've almost got yieldfrom working...

I've found one problem with that syntax: people use variables named "from" quite a lot in code already (including all over the coffeescript source)

"for of" is actively being added to V8. It should not be very long before it lands in V8 (and thus in Node). I don't like the idea of another keyword that at best acts exactly the same (or at worst acts subtly different).

CoffeeScript already has an of operator (like js in) and an in operator (array like iteration) neither of which could easily be made to both (I think). So we'd probably need a new name. Once "of" is in V8 we can compile to it directly though.

It's not clear to me how to compile directly to it without breaking CoffeeScript code that already uses for/of. Is the idea to break compatibility with existing CoffeeScript code?

See my longer question about this upthread.

I honestly don't know, this was just a quick hack this morning while I had a hangover :) I think it's good to have the conversation though!

I'm not current on what kind of compatibility coffeescript is trying to keep, but IE6 certainly not going to like the newer V8 features...

From the article:

> Update: I've created a PR [pull request] for CoffeeScript. I've also just added the yieldfrom keyword...

Maybe this update happened after your comment?

Yes, both updates happened after that comment. In fact that comment provided a little extra motivation for me to get those extra features done :)

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