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Date: Tue, 08 Nov 2016 14:25:13 +0200
To: David Walker <dave+php@mudsite.com>
Cc: internals@lists.php.net, Andrea Faulds <ajf@ajf.me>, Fleshgrinder
 <php@fleshgrinder.com>
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Subject: Re: [PHP-DEV] [RFC] Interval Comparison
From: lauri.kentta@gmail.com (=?UTF-8?Q?Lauri_Kentt=C3=A4?=)

On 2016-11-07 23:51, David Walker wrote:
> On Mon, Nov 7, 2016 at 1:38 PM Fleshgrinder <php@fleshgrinder.com> 
> wrote:
>> We are only extending binary to ternary for <= and <.
> 
> I realize that my comment, and question were going a bit off-topic with
> going on about the chaining of comparisons, but I'm interested in it 
> more
> because I wonder which would be harder to implement.  It would seem to 
> me
> that it would be harder to implement a means in which you only allow 
> one
> additional layer of comparison, rather than abstract chaining of
> comparisons (<, <=, >, >=).

I'm pretty sure that a three-part comparison is easier to implement. It 
can be kind of hard-coded as a new type of syntax, somewhat like the 
ternary operator.

Personally I'd prefer the full Python-style chaining. It's a lot more 
useful, especially for cases like 0 < $a <= $b < $upper_limit.

One possible implementation idea (not knowing anything about Zend): 
Comparison (a<b) would return a pair of data, the result and the latter 
value. If this was the last comparison or the result was false, the 
value will be dropped and the comparison ends. Else the result (true) 
will be dropped and the comparison will go on.

-- 
Lauri Kenttä