Re: [RFC] Interval Comparison

On Sat, Nov 12, 2016 at 3:08 AM Lauri Kenttä <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 = 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