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Date: Mon, 8 Apr 2019 13:53:46 +0200
Message-ID: <CAG9XoMRgcMLXAFC+VF0or0wa83s6G0TV3yeHp=zb1XgX8WNRyg@mail.gmail.com>
To: Stephen Reay <php-lists@koalephant.com>
Cc: Dan Ackroyd <Danack@basereality.com>, Guilliam Xavier <guilliam.xavier@gmail.com>, 
	PHP internals <internals@lists.php.net>, David Rodrigues <david.proweb@gmail.com>
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Subject: Re: [PHP-DEV] [RFC] Nullable Casting
From: benjamin.morel@gmail.com (Benjamin Morel)

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>  if your target =E2=80=99type=E2=80=99 is `?int` and you pass an empty st=
ring, wouldn=E2=80=99t
you expect to get `null` rather than `0` ?

I'd personally expect an `Error`, but this is not very much in line with
current casting semantics.

You have a point here, there is no clear answer for this edge case.

Maybe before nullable casting, should be discussed throwing errors when
attempting to cast a bad value, such as `(int) ""` ?
I think we're getting one step closer with the string to number comparison
RFC <https://wiki.php.net/rfc/string_to_number_comparison>, which suggests
that `"" !=3D "0"`.

Ben



On Mon, 8 Apr 2019 at 12:25, Stephen Reay <php-lists@koalephant.com> wrote:

>
> > On 8 Apr 2019, at 16:35, Benjamin Morel <benjamin.morel@gmail.com>
> wrote:
> >
> >> register_cast_function('?int', 'castToIntOrNull');
> >
> > I would quite oppose such a generic implementation, as it might have
> > unexpected consequences in other parts of the codebase : it's a global
> > configuration set at runtime.
> >
> > I quite like the idea of nullable casting though, as I've come across a
> few
> > cases myself where this would have been useful and would have made the
> code
> > more concise/readable.
> >
> > Ben
> >
> > On Mon, 8 Apr 2019 at 04:55, Dan Ackroyd <Danack@basereality.com> wrote=
:
> >
> >> On Sat, 6 Apr 2019 at 08:53, Guilliam Xavier <guilliam.xavier@gmail.co=
m
> >
> >> wrote:
> >>>
> >>> Hello internals,
> >>>
> >>> David and I would like to open the discussion on our joint RFC:
> >>>
> >>> https://wiki.php.net/rfc/nullable-casting
> >>>
> >>> Mainly, it would enable to use e.g. `(?int)$x` besides `(int)$x`.
> >>>
> >>
> >> I'm guessing you don't actually have ths function getIntOrNull() in
> >> your code-base? To help me understand where this would be useful,
> >> could you provide some 'real-world' code where this would be useful?
> >>
> >> By the way, this RFC is a special case of something that could be far
> >> more generic. If it was possible to register callbacks to be used when
> >> casting, people could do something like this:
> >>
> >> function castToIntOrNull($value)
> >> {
> >>    if ($value =3D=3D=3D null) {
> >>        return null;
> >>    }
> >>
> >>    return (int)$int;
> >> }
> >>
> >> register_cast_function('?int', 'castToIntOrNull');
> >>
> >> $x =3D (?int)getIntOrNull();
> >>
> >>
> >>> Additionally, it was requested on the mailing list to consider adding
> >>> support of nullable types to the settype() function,
> >>> e.g. settype($variable, "?int")
> >>
> >> Someone probably needs to make an argument for it to be in core,
> >> rather than just saying that it's something that could be done.
> >>
> >> cheers
> >> Dan
> >> Ack
> >>
> >> --
> >> PHP Internals - PHP Runtime Development Mailing List
> >> To unsubscribe, visit: http://www.php.net/unsub.php
> >>
> >>
>
> I=E2=80=99ve come across this pattern (string variable contains a number =
or
> nothing) myself, but it also then makes me think - if your target =E2=80=
=99type=E2=80=99 is
> `?int` and you pass an empty string, wouldn=E2=80=99t you expect to get `=
null`
> rather than `0` ?
>
>
>
>
>

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