On Sat, Nov 12, 2016 at 3:08 AM Lauri Kenttä <lauri.ken...@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 = 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 < $a++ && 3 < 3). I think the same would have
> > too somehow handle (either by syntax error or something) that if a
> > non-numeric value creeps into a binary-op-compare we error like: if
> > (1 < (2==3) < 3).
> >
> > Just some food for thought
> > --
> > Dave
>
> I don't see how you would ”logically” get 3 < 3. The very point of
> chaining is that each expression is evaluated only once, so the
> expression will have the same value in both of the comparisons. So if
> the first part is 1<2, then the other must be 2<3 (and not 3<3).
>
> An expression like a < b < c < d can be currently implemented with
> temporary variables like this:
> a < ($tmp1 = b) && $tmp1 < ($tmp2 = c) && $tmp2 < d
>
That's was the intent in the question I tried to raise with the
post-increment, as you write `$tmp1 = b`, to my example `$tmp1 = $a++`:
Should
$a = 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
```
$a = 0;
var_dump($a < 1);
var_dump(++$a < 1);
```
Would print out true, false.
Sorry I wasn't overly clear in my statement.
--
Dave
