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To: tyson andre <tysonandre775@hotmail.com>,
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Date: Tue, 1 Sep 2020 22:53:18 +0200
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Subject: Re: [PHP-DEV] [RFC] Global functions any() and all() on iterables
From: dik.takken@gmail.com (Dik Takken)

On 01-09-2020 01:56, tyson andre wrote:
> Hi internals,
> 
> I've created an RFC for https://wiki.php.net/rfc/any_all_on_iterable

Hi Andre,

I like the RFC, it is small and the added value is clear. The RFC
mentions the possibility of adding a first() method in the future. I
think it would be great to generalize this to the very thing that
excites me most about this RFC: It could be the starting point for
ultimately arriving at a better set of tools for working with iterables.

There is some discussion about the need for functions that work on keys
in stead of values or on both keys and values. It was suggested to
introduce option flags. It was also suggested to change the function
names to allow introducing multiple variants in the future:

  all_values()
  all_keys()

However, as Larry already hinted at, we may be able to do better. If we
introduce a keys() function that generates the keys from a given
iterable then we can use any value oriented function to work with the
keys in stead.

There is also the case where both the keys and values are relevant. It
may be interesting to look at how Python handles this (I'm sorry, I just
happen to know that language well). Python has dictionaries.
Dictionaries have an items() method. This method is one of the most
commonly used methods in Python. It is a generator that yields key/value
pairs, one pair for each item in the dictionary.

Perhaps we could do the same thing by introducing an items() function
that takes an iterable and yields one array for each item in the
iterable. The arrays contain the key/value pairs. Quoting the example
Tyson gave:

  any($itemMap, fn($enabled, $itemId) => $enabled &&
  meetsAdditionalCondition($itemId), ARRAY_FILTER_USE_BOTH)

Using items(), the above can also be written as:

  any(items($itemMap), fn($item) => $item[0] &&
  meetsAdditionalCondition($item[1]))

This way we can do with just one any() variant and without option flags.
It makes the example slightly less descriptive though, trading variable
names for array indices. In Python I would probably use a comprehension
here. Maybe the following will be possible in PHP at some point:

  any(foreach $itemMap as $enabled => $itemId yield $enabled &&
  meetsAdditionalCondition($itemId))

Regards,
Dik Takken