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Date: Wed, 10 Dec 2014 21:30:04 +0100
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Subject: AW: [PHP-DEV] [RFC] Nullsafe calls
From: php@tutteli.ch ("Robert Stoll")


> -----Urspr=FCngliche Nachricht-----
> Von: Josh Watzman [mailto:jwatzman@fb.com]
> Gesendet: Mittwoch, 10. Dezember 2014 19:43
> An: Robert Stoll
> Cc: PHP internals
> Betreff: Re: [PHP-DEV] [RFC] Nullsafe calls
>=20
> On Dec 10, 2014, at 8:17 AM, Robert Stoll <php@tutteli.ch> wrote:
>=20
> > First of all, I like the RFC, I think as well that it is a useful
> > feature for PHP and I already have it on my wish list
> > ;)
> >
> > Yet, either I misunderstand the section about short circuiting or I =
propose to change the behaviour.
> >
> > "If $obj is null, when $obj?->foo(..) executes, the arguments will =
still be evaluated."
> >
> > IMO that is wrong. It should not evaluate the arguments since the =
nullsafe operator (sometimes called "safe
navigation"
> > operator in other languages - which is the better wording IMO, maybe
> > change it? But that is just a detail) is just syntactic sugar for =
making the call only if $bj is not null. So the
following:
> >
> > [...]
> >
>=20
> Take a look at the "short circuit" section where I specifically =
address this. It was done to make it easier to reason
about in a
> side-effect-ful language like PHP. With this behavior, when you see
>=20
> $x?->f(g(), h())
>=20
> you don't have to worry about thinking whether g() and h() will =
actually be evaluated or not -- only the call to f()
itself,
> which is explicitly marked as nullsafe (i.e., might not happen). It =
also comes down to what you mean by "not making
the
> method call when $x is null" -- we in fact don't make the method call, =
but we still prepare everything as if we were
going to,
> and just decide not to do it at the last moment.
>=20
> I feel pretty strongly that this is the correct behavior. It may sound =
strange when talking about isolated examples
like this,
> but in the real-world code I've seen, it is the least confusing. (I'll =
see if I can dig up a better example instead of
just citing
> nebulous "real-world code" ;))
>=20
> Josh
>=20
>=20
> --
> PHP Internals - PHP Runtime Development Mailing List To unsubscribe, =
visit: http://www.php.net/unsub.php

I stick with it, evaluating it does not make sense IMO. If I want to =
execute it in any case then I would do something
like this currently

$g =3D g();
$h =3D h();
if($x !=3D=3D null){
  $x->foo($g, $h)->bar(baz());
}

And with the ?-> operator:

$g =3D g();
$h =3D h();
$x?->foo($g, $h)?->bar(baz());

Where I do not expect that baz() is called. You wrote it will be =
confusing for the user if the arguments would not be
evaluated. I do not think so, telling them it is a short form for ($x =
!=3D=3D null ? $x->foo() : null) is very easy and
straight forward for the user to pick up. Therefore, please dig up a =
better example. Right now,  I think it is a good
idea in general to add a nullsafe operator to PHP but not only in the =
way mentioned.