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Date: Tue, 26 Nov 2013 18:35:18 +0000
Message-ID: <CAOtgO62tg5EfikR2GCjvT1ji3RJWyvFbC1ioeraWowxpuDr2vw@mail.gmail.com>
To: internals@lists.php.net
Content-Type: multipart/alternative; boundary=047d7b2e4eda116b5704ec18be30
Subject: Re: [PHP-DEV] [Proposal] Modification to ?: functionality
From: jezzgoodwin@gmail.com (Jezz Goodwin)

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Content-Type: text/plain; charset=ISO-8859-1

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 = 'default';

or

isset($foo) ?: $foo = 'default';

(I personally prefer wrapping the condition within brackets)

Saying that, I do think a syntax for setting defaults which doesn't involve
typing the variable name twice would be nice.

My favourite one listed so far is:

$foo ?= 'default';


--
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.com>
> > wrote:
> >>
> >> On Tue, Nov 26, 2013 at 12:41 PM, Paul Dragoonis <dragoonis@gmail.com>
> >> 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.co>
> >> >> > wrote:
> >> >> >
> >> >> >> I believe these two statements are functionally equivalent:
> >> >> >>
> >> >> >> $foo = $foo ? $foo : 'default';
> >> >> >>
> >> >> >> $foo = $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:
> >> >> >>
> >> >> >> $foo = isset($foo) && $foo ? $foo : 'default';
> >> >> >>
> >> >> >> $foo = $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, lets
> 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 = $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 handle
> >> >> > 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 = $foo @: 'default';
> >> >>
> >> >> and possibly
> >> >>
> >> >> $foo @= '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 back
> >> >> > then.
> >> >> >
> >> >> > --mats
> >> >> >
> >> >>
> >>
> >> This seems like a cracking time to suggest:
> >>
> >>    $x ||= $y;
> >>
> >> The difference? Anything left of the ? SHOULD fail if it is not set,
> >> because you are using it in a condition which is dangerous and odd for
> >> other types of condition, but adding in this new syntax (similar to
> >> Ruby) would essentially evaluate to this:
> >>
> >>
> >>    empty($x) ? $y : $x;
> >>
> >> This gives keeps the behavior of ternary operators working in the same
> >> 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 = $x || $y like all the <OP>= binary operators.
> 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 = $x || $y but $x || $x = $y.
>
>
> http://www.rubyinside.com/what-rubys-double-pipe-or-equals-really-does-5488.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:
>
>      $foo = isset($foo) && $foo ? $foo : 'default';
>
> Proposed change by OP (with BC break):
>
>     $foo = $foo ?: 'default';
>
> New ternary suggested by others, with "error suppressing":
>
>     $foo = $foo ??: 'default';
>
> People will try using that with all sorts of other operators involved.
> What happens when you do  $foo = $foo == 'bar' ??: 'default'; It gets
> complicated.
>
>     $foo ||= '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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