Re: [boost] [Review:Algorithms] Order of args to clamp

Subject: Re: [boost] [Review:Algorithms] Order of args to clamp
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2011-09-26 13:40:20

Le 26/09/11 15:08, Stewart, Robert a écrit :
> Krzysztof Czainski wrote:
>> I'd like to add my version of clamp declaration. It might be a
>> compromise here:
>>
>> template<  class T, class L, class H>
>> T const&  clamp( T const&  x, L const&  lo,  H const&  hi );
> That's what I had wanted, though the return type cannot be a reference type (making the suggested "in-place" overload useful).  The introduction of common_type<T,L,H>  complicated matters too much, I think.  The idea of this version is simply that the type to clamp is T.
I'm not sure this is always the case. When I want to clip an 22 bit 
integer to a 16 bit integer, I expect the result be a 16 bit integer. So 
in these cases the result type will be the types of lo and hi. And in 
this case I can not convert the 22 bits integer to a 16 bit because I 
would lost some essential information.
>
> Off the top of my head:
>
>        template<class T, class L, class H>
>        T clamp(T const&  x, L const&  lo, H const&  hi);
>
>     Requires: x<  lo, hi<  x, T(lo), and T(hi) are well formed;
>               lo<= hi
>
>     Returns:  T(lo), if x<  lo; T(hi), if hi<  x; otherwise x

We could add specializations when the 3 parameters have the same type,

template<class T>
       T const&  clamp(T const&  x, T const&  lo, T const&  hi);

    Requires: x<  lo, hi<  x are well formed;
              lo<= hi

    Returns:  lo, if x<  lo; hi, if hi<  x; otherwise x

This will have the advantage to don't requiring the copy of the value.

Best,
Vicente