Re: [boost] [algorithm][minmax_element] implementation question

Subject: Re: [boost] [algorithm][minmax_element] implementation question
From: Marc Glisse (marc.glisse_at_[hidden])
Date: 2013-07-04 06:54:11

On Wed, 3 Jul 2013, Michael Marcin wrote:

> I was looking at minmax_elemement to try and understand the algorithm.
>
> I noticed that the boost implementation looks significantly more complicated 
> than the clang libc++ implementation.

It isn't that much longer...

> Mainly due to the potential_min_result variable that exists in the boost 
> version.

http://www.boost.org/doc/libs/1_54_0/libs/algorithm/minmax/
mentions why this variable exists.

> Is there a reason for this discrepancy? Is there a bug in the clang 
> implementation?

Maybe. Isn't there a test for minmax_element in the boost testsuite? 
(although I don't know if it specifically checks for the very particular 
case where potential_min_result is useful (2 equal consecutive values 
achieving the minimum, the first one with an even index, IIRC)).

Actually, reading the standard, it uses a different definition of 
minmax_element: the second element is not max_element but something like 
last_max_element.

-- 
Marc Glisse