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Date: Sat, 12 Nov 2016 16:21:32 +0000
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To: =?UTF-8?Q?Lauri_Kentt=C3=A4?= <lauri.kentta@gmail.com>
Cc: internals@lists.php.net, Andrea Faulds <ajf@ajf.me>
Content-Type: multipart/alternative; boundary=94eb2c11c9e895031605411d00ee
Subject: Re: [PHP-DEV] [RFC] Interval Comparison
From: dave+php@mudsite.com (David Walker)

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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 < $a++ && 3 < 3).  I think the same would have
> > too somehow handle (either by syntax error or something) that if a
> > non-numeric value creeps into a binary-op-compare we error like:  if
> > (1 < (2=3D=3D3) < 3).
> >
> > Just some food for thought
> > --
> > Dave
>
> I don't see how you would =E2=80=9Dlogically=E2=80=9D get 3 < 3. The very=
 point of
> chaining is that each expression is evaluated only once, so the
> expression will have the same value in both of the comparisons. So if
> the first part is 1<2, then the other must be 2<3 (and not 3<3).
>
> An expression like a < b < c < d can be currently implemented with
> temporary variables like this:
> a < ($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

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