Re: std::max: if versus ?:

[Marc Glisse <marc dot glisse at inria dot fr>]

On Thu, 20 Sep 2012, Marc Glisse wrote:

> Hello,
>
> I noticed that std::max is implemented as:
>
>      //return  __a < __b ? __b : __a;
>      if (__a < __b)
>        return __b;
>      return __a;
>
> Notice how it doesn't use the ?: code but the "if" version instead. Looking 
> at the history, this seems to come from SGI. Does someone know why it was 
> done this way?
>
> The reason I am asking is that if I add ?: support for vector types (à la 
> OpenCL), with "if" std::max will still fail on vectors, but with ?: it would 
> suddenly become accepted.

Hmm, I should have waited until I had at least a rough prototype to speak. 
std::max returns a reference to one of its arguments. For vectors, ?: 
produces an rvalue (it is an operator similar to & or |, except that it 
takes 3 arguments). So we have replaced code that failed to compile with 
code that (silently in my prototype) returns a reference to a temporary 
:-( Seems like if I want a std::max for vectors, I need to overload it...

--
Marc Glisse