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Reply-To: Levi Morrison <levi.morrison@datadoghq.com>
Date: Mon, 8 Feb 2021 17:48:32 -0700
Message-ID: <CAAKU0u=5ypeaT7u3xi-zT=cXLJxJYXrL_LLaV+HRXHmYSJWwOA@mail.gmail.com>
To: tyson andre <tysonandre775@hotmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [VOTE] PHP\iterable\any() and all() on iterables
From: internals@lists.php.net ("Levi Morrison via internals")

On Mon, Feb 8, 2021 at 5:15 PM tyson andre <tysonandre775@hotmail.com> wrot=
e:
>
> Hi Larry Garfield,
>
> > > Hi Larry Garfield,
> > >
> > > > > Hi internals,
> > > > >
> > > > > Voting has started on https://wiki.php.net/rfc/any_all_on_iterabl=
e and
> > > > > ends on 2021-02-22.
> > > > >
> > > > > This RFC proposes to add the functions `PHP\iterable\any(iterable
> > > > > $input, ?callable $callback =3D null): bool` and `PHP\iterable\al=
l(...)`
> > > > > to PHP's standard library's function set, using the namespace pre=
ferred
> > > > > in the previous straw poll.
> > > > >
> > > > > There is a primary vote on whether to add the functions, and a
> > > > > secondary vote on the name to use within the `PHP\iterable` names=
pace.
> > > > >
> > > > > Thanks,
> > > > > - Tyson
> > > > > --
> > > > > PHP Internals - PHP Runtime Development Mailing List
> > > > > To unsubscribe, visit: https://www.php.net/unsub.php
> > > >
> > > >
> > > > Ak!  I literally just finished reading it and wanted to note a lack=
 of clarity on one point. :-)
> > > >
> > > > The signature of the callback is never specified explicitly.  The t=
ernary is a bit confusing.  I assume the signature is
> > > >
> > > > callable(mixed): bool
> > > >
> > > > But that's not made explicit.  It's also not made explict that omit=
ting the callable collapses to "is truthy".  That's a sensible thing to do,=
 but it's not stated explicitly anywhere, just inferred from the code sampl=
e.
> > > >
> > > > I'm not sure if it's safe to clarify at this point as the vote just=
 started.
> > >
> > > If there is a callable, it allows `callable(mixed): mixed`,
> > > and converts the callable's return value to a boolean.
> > > So omitting the callable is the same as passing in the callable `fn($=
x)
> > > =3D> $x`, which is equivalent to `fn($x) =3D> (bool)$x`.
> > > This is exactly what the reference implementation would do.
> > >
> > > I definitely should have clarified it instead of assuming that the
> > > reference implementation was clear enough.
> > >
> > > I clarified this and gave examples because the RFC started a few hour=
s
> > > ago and the implementation didn't change.
> >
> > Oof.  I'm glad I asked, because I don't like that at all.  If available=
, the callable should be returning bool, not "anything that may be truthy/f=
alsy."  If you have an explicit function, it should have an explicit return=
 type.  A truthy check is a reasonable default, but not for when you're opt=
ing in to specifying the logic.
> >
> > I am in favor of the RFC, but I will have to consider if that changes m=
y vote to No.
> >
> > --Larry Garfield
>
> This was a deliberate choice and is consistent with the weak type compari=
son behavior of array_filter() and other functions that default to using we=
ak type checks internally.
>
> I'd agree that I'd prefer to see callbacks returning booleans in code I'm=
 reviewing,
> but a truthiness check seems more practical and consistent with the rest =
of the language
> than throwing a TypeError or checking the predicate return value using `!=
=3D=3D true`
>
> This was made to make PHP more widely accessible and free of surprises.
> e.g. `(bool)array_filter($arr, $predicate)` can be safely converted to `a=
ny($arr, $predicate)` without introducing a TypeError or behavior change.
>
> ```
> php > var_dump(array_filter([-1,0,1], fn($x)=3D>$x));
> array(2) {
>   [0]=3D>
>   int(-1)
>   [2]=3D>
>   int(1)
> }
> ```
>
> This is the same choice as many other dynamic languages that aren't compi=
led ahead of time have made.
>
> ```
> # python
> >>> any([1])
> True
> >>> any([0])
> False
> # Ruby
> irb(main):001:0> [nil].any?
> =3D> false
> irb(main):002:0> [false].any?
> =3D> false
> irb(main):003:0> !!0
> =3D> true
> irb(main):004:0> [0].any?
> =3D> true
> # JavaScript
> > [0].some(x=3D>x)
> false
> > [1].some(x=3D>x)
> true
> ```
>
> It is currently possible to check if code is passing a callable returning=
 anything other than a boolean
> to functions such as `array_filter()` using a wide variety of static anal=
yzers/tools, e.g. http://github.com/phan/phan
>
> ```
> <?php
> // Phan emits "PhanTypeMismatchArgumentInternal Argument 2 ($callback) is=
 (fn) of type Closure(int):int
> // but \array_filter() takes callable(mixed):bool|callable(mixed,mixed):b=
ool"
> array_filter([1], fn (int $x): int =3D> $x % 3);
> ```
>
> Thanks,
> -Tyson
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: https://www.php.net/unsub.php
>

For what it is worth, in C++ it is fairly normal to use a convertible
to bool type. For instance, having an overload on a < b for iterators
can return whatever type it wants, as long as it is contextually
convertible to bool.