Re: Generators (iterators) for Gnu Emacs

[Daniel Colascione]

On 12/05/2014 02:16 PM, Stefan Monnier wrote:
>> I think we could do so, though, apart from the definition, our packages
>> seem quite disjoint.
> 
> I prefer to look at it as "complementary".
> 
>> Anyway, it would be good if Daniel's generators would then be valid
>> iterators in terms of the new iterator.el.
> 
> Indeed, that would be nice.  Can you try and work that out?

Assuming both packages are suitable for inclusion into core, we can definitely 
make them work together. I'd still very much like to use nonlocal control flow 
instead of a sentinel for enumeration termination, however.  

That aside, I'm not sure I agree with your namespace preferences. `yield' is 
fundamentally a lexically-scoped macro. Making it defer to some prior 
definition makes no sense, since any code that can see this macro is already 
written with generators in mind.

I'd also strongly prefer using `next' as the iter-get function. If we're going 
to make the iteration protocol a core part of the environment, it deserves a 
prominent place in the global namespace. Using `funcall' is inadequate: first, 
it doesn't signal iteration in calling code, which can lead to confusion, and 
second, `funcall' doesn't work if we want to extent `next' to support things 
like lists, for which `next' would be equivalent to `pop'. AFAICT, nothing is 
already squatting on `next', so binding the symbol's function slot would be 
harmless for a compatibility perspective.

I'd also prefer using `iterating' as the cl-loop keyword. Because the keyword 
is only active in the lexical scope of a cl-loop construct, there's an even 
lower risk of collision, and the word "iterating" is exactly the right thing in 
the cl-loop language: (cl-loop for x iterating y collect x) reads very well.

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