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Date: Mon, 31 Oct 2016 16:49:01 -0500
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Subject: Re: [PHP-DEV] Allow Iterator to be used with current, next, reset,
 key functions
From: larry@garfieldtech.com (Larry Garfield)

On 10/31/2016 01:07 PM, Levi Morrison wrote:
> On Mon, Oct 31, 2016 at 11:57 AM, Levi Morrison <levim@php.net> wrote:
>> On Mon, Oct 31, 2016 at 11:27 AM, Larry Garfield <larry@garfieldtech.com> wrote:
>>> Question: Now that we have "iterable" as a type, should we be adding more
>>> array-specific functions or should such operations be designed, and named,
>>> to operate on any iterable?  (first(), first_key(), etc.)
>> At least for last and last-key I do not think we should make them work
>> with any iterable. My reasoning is that we do not want to consume the
>> iterator for them because many iterators are not rewindable (such as
>> generators). The first and first-key routines should generally work
>> because `rewind(); valid(); current(); rewind();` doesn't contain a
>> `next()` call.
>>
>> Rewinding without iterating works for generators: https://3v4l.org/O7ZKO
>> Rewinding after a next() call: https://3v4l.org/QI434
> Additionally consuming the iterator would be an algorithmic complexity
> of O(n) whereas for an array would just be O(1). So not only is it
> annoying that the iterator is consumed and can't be guaranteed to be
> rewound it is also costly.
>
> The first and first-key routines do not have these issues.


Might it make sense then to have

first(iterable)
first_key(iterable)
array_last(array)
array_last_key(array)

It's not quite as parallel, but it does provide more broadly compatible 
functionality.

If we're concerned about pw0ning the "first" function name, perhaps it's 
time to start a new prefix:

iter_first(iterable)
iter_first_key(iterable)
array_last(array)
array_last_key(array)

Which gives a natural place to start putting iterable-friendly 
alternates of the various array_* functions, for those that make sense.  
(think iter_fold(), iter_map(), iter_filter(), etc.)

(Insert debate about parameter order and method-based alternatives here.)

--Larry Garfield