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In-Reply-To: <ba85b729-0a8c-d0b2-a765-f3830e8131b0@fleshgrinder.com>
Date: Fri, 11 Nov 2016 17:03:45 +0000
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To: internals@lists.php.net, Andrea Faulds <ajf@ajf.me>, lauri.kentta@gmail.com
Content-Type: multipart/alternative; boundary=001a11440feeacfe11054109793f
Subject: Re: [PHP-DEV] [RFC] Interval Comparison
From: dave+php@mudsite.com (David Walker)

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On Wed, Nov 9, 2016 at 12:48 PM Fleshgrinder <php@fleshgrinder.com> wrote:

> On 11/8/2016 10:57 PM, David Walker wrote:
> > I don't think that alone allows the chaining of comparisons.  I'd have to
> > look closer, but it'd seem to me that zend_ast_create_binary_op
> > (ZEND_AST_BINARY_OP) evaluation might need to be amended as well.  Seems
> it
> > eventually calls a `op(zval*,zval*,zval*) so the evaluated end of: one op
> > would be a true/false, when comparing against another boolean op.
> >
> > Regardless of implementation, the core question you raised was should
> > something like it exist, I'm still a strong yes on that front.  I'd just
> > promote introducing the left precedence and allowing the arbitrary chains
> > of comparison, rather than just a single interval comparison.
> >
> > cheers
> > --
> > Dave
> >
>
> Yeah maybe not that easy but also not too complicated if we add
> associativity to the mix. I am open for both variations and could write
> up an RFC with a vote for both if desired.
>
> Not sure if I find the time to look into actual implementation but I
> most certainly can try.
>

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

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