Tiny Vector Matrix library using Expression Templates

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include/tvmet/TypePromotion.h

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/*
 * Tiny Vector Matrix Library
 * Dense Vector Matrix Libary of Tiny size using Expression Templates
 *
 * Copyright (C) 2001 - 2007 Olaf Petzold <opetzold@users.sourceforge.net>
 *
 * This library 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.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: TypePromotion.h,v 1.10 2007-06-23 15:58:58 opetzold Exp $
 */

#ifndef TVMET_TYPE_PROMOTION_H
#define TVMET_TYPE_PROMOTION_H

namespace tvmet {


template<class T>
struct PrecisionTraits {
  enum {
    rank = 0,     
    known = 0       
  };
};


#define TVMET_PRECISION(T,R)                \
template<>                                    \
struct PrecisionTraits< T > {                 \
  enum {                                    \
    rank = R,                             \
    known = 1                             \
  };                                        \
};


/*
 * pod types
 */
TVMET_PRECISION(int, 100)
TVMET_PRECISION(unsigned int, 200)
TVMET_PRECISION(long, 300)
TVMET_PRECISION(unsigned long, 400)

#if defined(TVMET_HAVE_LONG_LONG)
TVMET_PRECISION(long long, 500)
TVMET_PRECISION(unsigned long long, 600)
#endif // defined(TVMET_HAVE_LONG_LONG)

TVMET_PRECISION(float, 700)
TVMET_PRECISION(double, 800)

#if defined(TVMET_HAVE_LONG_DOUBLE)
TVMET_PRECISION(long double, 900)
#endif // defined(TVMET_HAVE_LONG_DOUBLE)


/*
 * complex types
 */
#if defined(TVMET_HAVE_COMPLEX)
TVMET_PRECISION(std::complex<int>, 1000)
TVMET_PRECISION(std::complex<unsigned int>, 1100)
TVMET_PRECISION(std::complex<long>, 1200)
TVMET_PRECISION(std::complex<unsigned long>, 1300)

#if defined(TVMET_HAVE_LONG_LONG)
TVMET_PRECISION(std::complex<long long>, 1400)
TVMET_PRECISION(std::complex<unsigned long long>, 1500)
#endif // defined(TVMET_HAVE_LONG_LONG)

TVMET_PRECISION(std::complex<float>, 1600)
TVMET_PRECISION(std::complex<double>, 1700)

#if defined(TVMET_HAVE_LONG_DOUBLE)
TVMET_PRECISION(std::complex<long double>, 1800)
#endif // defined(TVMET_HAVE_LONG_DOUBLE)

#endif // defined(TVMET_HAVE_COMPLEX)


#undef TVMET_PRECISION


template<class T>
struct AutopromoteTraits {
  typedef T value_type;
};


/*
 * Defines a macro for specializing/defining
 * the promotion traits. bool, char, unsigned char, short int, etc. will
 * be autopromote to int, as in C and C++.
 */
#define TVMET_AUTOPROMOTE(T1,T2)            \
template<>                                    \
struct AutopromoteTraits<T1> {              \
  typedef T2 value_type;                    \
};

TVMET_AUTOPROMOTE(bool, int)
TVMET_AUTOPROMOTE(char, int)
TVMET_AUTOPROMOTE(unsigned char, int)
TVMET_AUTOPROMOTE(short int, int)
TVMET_AUTOPROMOTE(short unsigned int, unsigned int)

#undef TVMET_AUTOPROMOTE


template<class T1, class T2, int promoteToT1>
struct promoteTo {
  typedef T1 value_type;
};


template<class T1, class T2>
struct promoteTo<T1,T2,0> {
  typedef T2 value_type;
};


template<class T1org, class T2org>
class PromoteTraits {
  // Handle promotion of small integers to int/unsigned int
  typedef typename AutopromoteTraits<T1org>::value_type T1;
  typedef typename AutopromoteTraits<T2org>::value_type T2;

  enum {
    // True if T1 is higher ranked
    T1IsBetter = int(PrecisionTraits<T1>::rank) > int(PrecisionTraits<T2>::rank),

    // True if we know ranks for both T1 and T2
    knowBothRanks = PrecisionTraits<T1>::known && PrecisionTraits<T2>::known,

    // True if we know T1 but not T2
    knowT1butNotT2 = PrecisionTraits<T1>::known && !(PrecisionTraits<T2>::known),

    // True if we know T2 but not T1
    knowT2butNotT1 =  PrecisionTraits<T2>::known && !(PrecisionTraits<T1>::known),

    // True if T1 is bigger than T2
    T1IsLarger = sizeof(T1) >= sizeof(T2),

    // We know T1 but not T2: true
    // We know T2 but not T1: false
    // Otherwise, if T1 is bigger than T2: true
    defaultPromotion = knowT1butNotT2 ? false : (knowT2butNotT1 ? true : T1IsLarger),

    // If we have both ranks, then use them.
    // If we have only one rank, then use the unknown type.
    // If we have neither rank, then promote to the larger type.
    promoteToT1 = (knowBothRanks ? T1IsBetter : defaultPromotion) ? 1 : 0
  };

 public:
  typedef typename promoteTo<T1,T2,promoteToT1>::value_type value_type;
};


} // namespace tvmet

#endif // TVMET_TYPE_PROMOTION_H

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