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

Subject: Re: [boost] [Review:Algorithms] Order of args to clamp
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-09-26 09:08:09

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.

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

      template <class T, class L, class H, class P>
      T clamp(T const & x, L const & lo, H const & hi, P p);

   Requires: p(x, lo), p(hi, x), T(lo), and T(hi) are well
             formed; lo <= hi

   Returns:  T(lo), if p(x, lo); T(hi), if p(hi, x); otherwise x

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

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

   Effects:  x = lo, if x < lo; x = hi, if hi < x; otherwise x
             unchanged

   Returns: x

      template <class T, class L, class H, class P>
      T & clamp(T & x, L const & lo, H const & hi, P p);

   Requires: p(x, lo), p(hi, x), x = lo, and x = hi are well
             formed; lo <= hi

   Effects:  x = lo, if p(x, lo); x = hi, if p(hi, x); otherwise
             x unchanged

   Returns: x

I'm sure some of that can be expressed more properly, but I think the idea is sufficiently well captured.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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