Generator use-cases

Brendan Eich brendan at
Sun Mar 30 12:08:39 PDT 2008

On Mar 30, 2008, at 10:58 AM, Jason Orendorff wrote:

> On Fri, Mar 28, 2008 at 10:32 PM, Brendan Eich  
> <brendan at> wrote:
>> This is a long-ish case for including generators in ES4 as proposed.
>> [...]
> Here's a brief case:  generators let you factor a complex loop,
> dividing the value-producing part from the value-consuming part.
> Neither part has to be transformed in a non-obvious way.  With
> iterators alone, you do this by rewriting the value-producing part as
> an Iterator class.  This obfuscates the iterator implementation.

Thanks, this is nice and short. I wanted to give example links and  
excerpts for those new to generators, but what you wrote here is a  
great summary and intro.

BTW, no single nominal Iterator class or interface is required, of  
course -- all you need is an object 'like IteratorType'.

> It's hardly news that abstracting from sequences is useful.  Various
> languages have had iterators, streams, and lazy lists as core,
> essential features (with syntactic support) for decades now.  For
> stateful languages, like Python and C#, iterators and generators fill
> this gap better than anything else I've seen.


> Adobe's position paper commented about generators not being that
> useful, because they're not "deep", like full coroutines.

Not to worry, Adobe is on board:

(I hope this is publicly readable -- it should be).


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