Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:96858
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.218.51 as permitted sender)
MIME-Version: 1.0
In-Reply-To: <CADVQu1Qfr6t76UHzDcZQ5809t4CDesS0WvAPgdN+gFCCV6_7Og@mail.gmail.com>
References: <cb36a781-9fed-2366-af7d-f3720af7a542@fleshgrinder.com>
 <CAEsg9X3Vdhi=GX=d5wcc=vMOA8-YCF9YoAZWU95ZPNxD7MYYKA@mail.gmail.com>
 <CADVQu1RQCcTN+LKJtDb8p2a1DZi9hwKqu5r80YmBJ=9NW+H3GA@mail.gmail.com>
 <d819c6c9-391b-88ca-5b3b-e4c04de33b7a@fleshgrinder.com> <CADVQu1Sk99bYJHeaALXSsETi3FqOVEU99v+Gd5PU0qktO2Wigg@mail.gmail.com>
 <3e3180e8-e9c2-abca-5228-221f8eae713d@fleshgrinder.com> <CADVQu1R=N=mKsmOcOoBnsvPo_1tg3nKLUN5si-_eg_wSFwyZdg@mail.gmail.com>
 <ba85b729-0a8c-d0b2-a765-f3830e8131b0@fleshgrinder.com> <CADVQu1T0DYHRzdJJ7mcjpA=CNMiLsJjwYjqBtKqs4XO8zUQ71Q@mail.gmail.com>
 <9a84054848086fa4c2965f93dd3b56a3@gmail.com> <CADVQu1Qfr6t76UHzDcZQ5809t4CDesS0WvAPgdN+gFCCV6_7Og@mail.gmail.com>
Date: Sat, 12 Nov 2016 08:27:43 -0800
Message-ID: <CAKOpQSzsv0iGfYWkmx3iU+8vRiCG0tw5Wh3dLf6wS8Wg7X0gow@mail.gmail.com>
To: David Walker <dave+php@mudsite.com>
Cc: Andrew Faulds <ajf@ajf.me>, PHP internals list <internals@lists.php.net>, 
	=?UTF-8?Q?Lauri_Kentt=C3=A4?= <lauri.kentta@gmail.com>
Content-Type: multipart/alternative; boundary=94eb2c095f7a2108e405411d16e1
Subject: Re: [PHP-DEV] [RFC] Interval Comparison
From: kris.craig@gmail.com (Kris Craig)

--94eb2c095f7a2108e405411d16e1
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

On Nov 12, 2016 8:21 AM, "David Walker" <dave+php@mudsite.com> wrote:
>
> On Sat, Nov 12, 2016 at 3:08 AM Lauri Kentt=C3=A4 <lauri.kentta@gmail.com=
>
wrote:
>
> > On 2016-11-11 19:03, David Walker wrote:
> > >
> > > I took a quick stab at implementing, and had something working for
> > > constant expressions, but handling something akin to:
> > >
> > > $a =3D 2;
> > > if (1 < $a++ < 3) {
> > > ...
> > > }
> > >
> > > Is a bit awkward in our expansions of : if (1 < $a++ && $a++ < 3).
> > > Seems as if when processing the chain here, you'd need to see if the
> > > left node has a child, and somehow ensure you get the evaluated value
> > > somehow, to override the "left" node.  So logically expansion of the
> > > above would be  if (1 < $a++ && 3 < 3).  I think the same would have
> > > too somehow handle (either by syntax error or something) that if a
> > > non-numeric value creeps into a binary-op-compare we error like:  if
> > > (1 < (2=3D=3D3) < 3).
> > >
> > > Just some food for thought
> > > --
> > > Dave
> >
> > I don't see how you would =E2=80=9Dlogically=E2=80=9D get 3 < 3. The ve=
ry point of
> > chaining is that each expression is evaluated only once, so the
> > expression will have the same value in both of the comparisons. So if
> > the first part is 1<2, then the other must be 2<3 (and not 3<3).
> >
> > An expression like a < b < c < d can be currently implemented with
> > temporary variables like this:
> > a < ($tmp1 =3D b) && $tmp1 < ($tmp2 =3D c) && $tmp2 < d
> >
>
> That's was the intent in the question I tried to raise with the
> post-increment, as you write `$tmp1 =3D b`, to my example `$tmp1 =3D $a++=
`:
>
> Should
> $a =3D 1;
> var_dump(1 < $a++ < 3);
>
> (expanded into numbers) be evaluated as:
> 1 < 2 && 2 < 3 - True
> or
> 1 < 2 && 3 < 3 - False
>
> I could see the case for either, although, I would probably prefer the
> latter, as that's what's apparent today, example with
>
> ```
> $a =3D 0;
> var_dump($a < 1);
> var_dump(++$a < 1);
> ```
>
> Would print out true, false.
>
> Sorry I wasn't overly clear in my statement.
> --
> Dave

+1 on the usefulness of this idea.  I've always wondered why more parsers
don't already support this.

--Kris

--94eb2c095f7a2108e405411d16e1--