Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:96748
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain mudsite.com designates 209.85.213.44 as permitted sender)
MIME-Version: 1.0
References: <cb36a781-9fed-2366-af7d-f3720af7a542@fleshgrinder.com> <CAEsg9X3Vdhi=GX=d5wcc=vMOA8-YCF9YoAZWU95ZPNxD7MYYKA@mail.gmail.com>
In-Reply-To: <CAEsg9X3Vdhi=GX=d5wcc=vMOA8-YCF9YoAZWU95ZPNxD7MYYKA@mail.gmail.com>
Date: Sun, 06 Nov 2016 21:43:55 +0000
Message-ID: <CADVQu1RQCcTN+LKJtDb8p2a1DZi9hwKqu5r80YmBJ=9NW+H3GA@mail.gmail.com>
To: David Rodrigues <david.proweb@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a114dcec27cae160540a8ce70
Subject: Re: [PHP-DEV] [RFC] Interval Comparison
From: dave+php@mudsite.com (David Walker)

--001a114dcec27cae160540a8ce70
Content-Type: text/plain; charset=UTF-8

On Sun, Nov 6, 2016 at 1:59 PM David Rodrigues <david.proweb@gmail.com>
wrote:

> I guess that the biggest problem is about the code parsing. Currently PHP
> should supports what you wrote, but with another meaning. And personally I
> think that this feature is not too common on programming language in
> general, once that it is possible from first format (maybe more clear too).
>
> Em 6 de nov de 2016 6:30 PM, "Fleshgrinder" <php@fleshgrinder.com>
> escreveu:
>
> > Validating whether a number is within a closed or open interval is
> > currently possible only via a construct like the following:
> >
> > ```
> > if (0 < $x && $x < 42) {
> >     echo 'x is in (0, 42)';
> > }
> >
> > if (0 <= $x && $x <= 42) {
> >     echo 'x is in [0, 42]';
> > }
> > ```
> >
> > It is not very readable and repetitive. It would be interesting to
> > support a more mathematical notation for this:
> >
> > ```
> > if (0 < $x < 42) {
> >     echo 'x is in (0, 42)';
> > }
> >
> > if (0 <= $x <= 42) {
> >     echo 'x is in [0, 42]';
> > }
> > ```
> >
>
>
Richard,

I'd be a +1 on this.  I dislike having the double comparison all over
checking for bounds, and have for quite a while. Akin to what David brought
up, https://3v4l.org/7MvlB.  It seems the requested syntax is not valid in
any PHP version testable here.  I can't speak to the complexities of
implementing something like that, but would find it useful.

Of course, you'd have to worry about other conditions like
```
if (0 < $x > 20)
```
By worry about, I mean, should it be invalid syntax, or, should it be
optimized to be `20 < $x`?  I'd say you'd have to maintain the gt/lt for
chaining.

Then I'd wonder about similar syntax to check if 2 variables are both
greater than 0, but one greater/equal to the other:
```
if (0 < $x <= $y)
```

--
Dave

--001a114dcec27cae160540a8ce70--