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Date: Sun, 10 Apr 2011 01:09:16 +0200
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To: Sanford Whiteman <swhitemanlistens-software@cypressintegrated.com>, 
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Subject: Re: [PHP-DEV] Implicit isset/isempty check on short-ternary operator
From: keisial@gmail.com ("=?ISO-8859-1?Q?=C1ngel_Gonz=E1lez?=")

Sanford Whiteman wrote:
> Same here.
>
> Here's my take:
>
> [1]  I  don't like ?? / ? because it is disjunctive with === / ==.. The
> extra  equals  sign  strengthens  equality comparison, while the extra
> question  mark  essentially  _weakens_ the ternary operator (making it
> more forgiving). (Sure, a case could be made that an "extra" duplicate
> operator has no inherent meaning overall, but these two operators seem
> to be in a similar domain.)
I disagree. They both reinforce the operator.
The = character means equivalence. == means that it is equal, === means
that it is very very equal.
The ? character means uncertainity, doubt. A single ? in a ternary
operator means a question (if() construct).
A ?? would not only mean is this true? but also does it even exists?
It also looks strange to my code parser (looks like a wtf comment) but
I'd probably adapt to that new operator easily.


> [4]  Strange  idea:  what about treating the variable as defined after
> you  test it with the special operator, even if you don't specifically
> assign it a value?
>
> So:
>
> $varor2  =  $var1  @?:  2  //  $varor2==2,  no warning because special
> ternary is used
>
> $varor3  =  $var1  ?: 3 // $varor3=3, but no warning because $var1 has
> been implicitly defined in special expression

This looks like a source for all kind of side-effects to me. I'm not
even convinced
that testing for raw variables would be useful. I think the usecase is
for testing arrays.


> [5]  Sort  of  the opposite of [4] and continuing the question of [3],
> what  about  only letting a variable be special-op-checked once before
> throwing  a  warning. So you can suppress (or not throw) the undefined
> warning  once,  but it is assumed that you will define the variable in
> that  statement.  So  this  would discourage the continuous use of the
> same  undef var throughout code (which seems like a code smell), while
> allowing  for the real case that you're using the special-op to filter
> $_REQUEST or whatever -- one time.
Tests shouldn't have side effects. Allowing the special-op one time, means
that the addition of a check in one place will start spewing in a
completely
different place of the codebase.
The way of forcing the users to set the undefined variable in one check is
not keeping a track if they have used a magic operation to check it and
didn't
set it after that, but defining a set-value-if-unset operator.
A syntax like ?=  looks like a set-if-set, so perhaps it would be more
appropiate
using !?=


> I  haven't  really  thought about the edges, but thought I'd put those
> out there.
Thanks for sharing!