Constraints.hh

/* 
This file is part of the BIAS library (Basic ImageAlgorithmS).

Copyright (C) 2003-2009    (see file CONTACT for details)
Multimediale Systeme der Informationsverarbeitung
Institut fuer Informatik
Christian-Albrechts-Universitaet Kiel


BIAS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

BIAS is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with BIAS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

namespace BIAS {

  /** @brief compile time check if B is (grand)father of T
  Found it in Bjarne Stroustrup's FAQ:
  http://public.research.att.com/~bs/bs_faq2.html
  "Actually, Derived_from doesn't check derivation, but conversion, but 
  that's often a better constaint. Finding good names for constraints
  can be hard."
  @author woelk 02/2006 */
  template<class T, class B> 
  class DerivedFrom 
  {
  public:
    static void Constraints(T* p) 
    { 
      B* pb = p; 
      pb=0 /*NULL*/; 
    }

    DerivedFrom() { 
      void(*p)(T*) = Constraints; 
      p=0 /*NULL*/; 
    }
  };

  /** @brief compile time check for copy compatibilty between T1 and T2
  Found it in Bjarne Stroustrup's FAQ:
  http://public.research.att.com/~bs/bs_faq2.html
  @author woelk 02/2006 */
  template<class T1, class T2> 
  class CanCopy 
  {
  public:
    static void Constraints(T1 a, T2 b) { T2 c = a; b = a; }
    CanCopy() { 
      void(*p)(T1,T2) = Constraints; 
      p=0 /*NULL*/; 
    }
  };

  /** @brief compile time check for comparabilty of T1 and T2
  Found it in Bjarne Stroustrup's FAQ:
  http://public.research.att.com/~bs/bs_faq2.html
  @author woelk 02/2006 */
  template<class T1, class T2 = T1> 
  class CanCompare 
  {
  public:
    static void Constraints(T1 a, T2 b) { a==b; a!=b; a<b; }
    CanCompare() { 
      void(*p)(T1,T2) = Constraints; 
      p=0 /*NULL*/; 
    }
  };

  /** @brief compile time check if T1 can be multiplied by T2
  Found it in Bjarne Stroustrup's FAQ:
  http://public.research.att.com/~bs/bs_faq2.html
  @author woelk 02/2006 */
  template<class T1, class T2, class T3 = T1> 
  class CanMultiply 
  {
  public:
    static void Constraints(T1 a, T2 b, T3 c) { c = a*b; }
    CanMultiply() { 
      void(*p)(T1,T2,T3) = Constraints; 
      p=0 /*NULL*/; 
    }
  };
}