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Date: Tue, 26 Nov 2013 19:46:36 +0000
Message-ID: <CAPg3XxKvVQVOzcJYujSyU-Ws=_dD+pvpqy+1xANMtQ+jde66qA@mail.gmail.com>
To: Jezz Goodwin <jezzgoodwin@gmail.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a11c2fa0674ae1104ec19bf36
Subject: Re: [PHP-DEV] [Proposal] Modification to ?: functionality
From: petercowburn@gmail.com (Peter Cowburn)

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On 26 November 2013 18:35, Jezz Goodwin <jezzgoodwin@gmail.com> wrote:

> Hi,
>
> Before mentioning anything about new syntax, I thought I'd point out that
> this code is already possible for setting defaults:
>
> (isset($foo)) ?: $foo =3D 'default';
>
> or
>
> isset($foo) ?: $foo =3D 'default';
>
> (I personally prefer wrapping the condition within brackets)
>
> Saying that, I do think a syntax for setting defaults which doesn't invol=
ve
> typing the variable name twice would be nice.
>
> My favourite one listed so far is:
>
> $foo ?=3D 'default';
>

I like that too.

Elaborating on that idea, here=92s one idea from a while back, making much
wider use of a =93?=94 operator=85 https://gist.github.com/salathe/3256826


>
>
> --
> Jezz
>
>
> On Tue, Nov 26, 2013 at 6:23 PM, Philip Sturgeon <pjsturgeon@gmail.com
> >wrote:
>
> > On Tue, Nov 26, 2013 at 1:08 PM, Etienne Kneuss <colder@php.net> wrote:
> > >
> > >
> > >
> > > On Tue, Nov 26, 2013 at 6:57 PM, Philip Sturgeon <pjsturgeon@gmail.co=
m
> >
> > > wrote:
> > >>
> > >> On Tue, Nov 26, 2013 at 12:41 PM, Paul Dragoonis <dragoonis@gmail.co=
m
> >
> > >> wrote:
> > >> > On Tue, Nov 26, 2013 at 4:58 PM, Chris London <me@chrislondon.co>
> > wrote:
> > >> >
> > >> >> On Tue, Nov 26, 2013 at 8:15 AM, Mats Lindh <mats.lindh@gmail.com=
>
> > >> >> wrote:
> > >> >>
> > >> >> > On Tue, Nov 26, 2013 at 3:43 PM, Chris London <me@chrislondon.c=
o
> >
> > >> >> > wrote:
> > >> >> >
> > >> >> >> I believe these two statements are functionally equivalent:
> > >> >> >>
> > >> >> >> $foo =3D $foo ? $foo : 'default';
> > >> >> >>
> > >> >> >> $foo =3D $foo ?: 'default';
> > >> >> >>
> > >> >> >
> > >> >> > They are.
> > >> >> >
> > >> >> >
> > >> >> > I would like to change it so it also checks for isset() so I
> > propose
> > >> >> > the
> > >> >> >> following would be functionally equivalent:
> > >> >> >>
> > >> >> >> $foo =3D isset($foo) && $foo ? $foo : 'default';
> > >> >> >>
> > >> >> >> $foo =3D $foo ?: 'default';
> > >> >> >>
> > >> >>
> > >> >
> > >> > We can't change the behaviour of ?: that ship has already sailed,
> > we'll
> > >> > just be hurting existing codebases on upgrading and more user
> > education
> > >> > is
> > >> > required to understand non-visual changes in syntax like this, let=
s
> > try
> > >> > to
> > >> > learn from our mistakes by not changing 'behaviour' anymore.
> > >> >
> > >> > An alternative syntax that is similar and not ugly would be good
> since
> > >> > the
> > >> > ?: behaviour was broken from the start since you still need to run
> > >> > isset()
> > >> > before running ?: which was the problem we tried to solve in the
> first
> > >> > place but it just didn't happen.
> > >> >
> > >> > I don't like the @ symbol it's too different from what's already
> there
> > >> > on
> > >> > the ternary logic.
> > >> >
> > >> > Proposal:   $foo =3D $arr['value'] ?:: "";
> > >> >
> > >> > Thoughts?
> > >> >
> > >> >>
> > >> >> > The would break the assumption that a reference to an
> uninitialized
> > >> >> > value
> > >> >> > would generate a notice, unless explicitly handled in the logic=
.
> > >> >> >
> > >> >> > While I also would like to have something similar to ?: to hand=
le
> > >> >> > default
> > >> >> > values for array keys, etc., this would change a fundamental
> > >> >> > assumption
> > >> >> > that as been in place for many years now. I'm not sure if that'=
s
> a
> > BC
> > >> >> break
> > >> >> > that would be acceptable this late. An alternative operator may
> be
> > >> >> > more
> > >> >> > suitable.
> > >> >> >
> > >> >>
> > >> >> What do you think about using:
> > >> >>
> > >> >> $foo =3D $foo @: 'default';
> > >> >>
> > >> >> and possibly
> > >> >>
> > >> >> $foo @=3D 'default';
> > >> >>
> > >> >>
> > >> >>
> > >> >> >
> > >> >> > The change proposed has also been discussed several times since
> the
> > >> >> > implementation of ?:. See the ifsetor-RFC:
> > >> >> >
> > >> >> > https://wiki.php.net/rfc/ifsetor
> > >> >> >
> > >> >> > It also contains links to the discussion around the feature bac=
k
> > >> >> > then.
> > >> >> >
> > >> >> > --mats
> > >> >> >
> > >> >>
> > >>
> > >> This seems like a cracking time to suggest:
> > >>
> > >>    $x ||=3D $y;
> > >>
> > >> The difference? Anything left of the ? SHOULD fail if it is not set,
> > >> because you are using it in a condition which is dangerous and odd f=
or
> > >> other types of condition, but adding in this new syntax (similar to
> > >> Ruby) would essentially evaluate to this:
> > >>
> > >>
> > >>    empty($x) ? $y : $x;
> > >>
> > >> This gives keeps the behavior of ternary operators working in the sa=
me
> > >> way, but adds what we want: the ability to nicely set defaults for
> > >> variables and array keys that may not be set.
> > >
> > >
> > > To me this reads as $x =3D $x || $y like all the <OP>=3D binary opera=
tors.
> > So it
> > > would definitely feel weird to use that syntax for something else...
> > >
> > >>
> > >>
> > >> --
> > >> PHP Internals - PHP Runtime Development Mailing List
> > >> To unsubscribe, visit: http://www.php.net/unsub.php
> > >>
> > >
> > >
> > >
> > > --
> > > Etienne Kneuss
> > > http://www.colder.ch
> >
> > It is not $x =3D $x || $y but $x || $x =3D $y.
> >
> >
> >
> http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-54=
88.html
> >
> > Ternary is being used by us to set defaults, but it is not the only
> > use of ternary, so making it totally quieten potential warnings and
> > errors is a weird use of a ternary. It's one of those "we do it this
> > way because its all we have" options and going further down the road
> > of abusing ternaries for this functionality does not make the
> > situation more simple.
> >
> > Currently:
> >
> >      $foo =3D isset($foo) && $foo ? $foo : 'default';
> >
> > Proposed change by OP (with BC break):
> >
> >     $foo =3D $foo ?: 'default';
> >
> > New ternary suggested by others, with "error suppressing":
> >
> >     $foo =3D $foo ??: 'default';
> >
> > People will try using that with all sorts of other operators involved.
> > What happens when you do  $foo =3D $foo =3D=3D 'bar' ??: 'default'; It =
gets
> > complicated.
> >
> >     $foo ||=3D 'default';
> >
> > Pretty obvious what is happening. If foo is falsey it will use
> > 'default'. We can wrap $foo in isset or empty and make it more
> > durable, which certainly would take care of the OP's concerns without
> > breaking the way ternaries currently work - which is not actually
> > broken just not very handy at setting defaults for non-existent
> > variables.
> >
> > --
> > PHP Internals - PHP Runtime Development Mailing List
> > To unsubscribe, visit: http://www.php.net/unsub.php
> >
> >
>

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