eigen/tvmet-1.7.1/include/tvmet/CommaInitializer.h

/*
 * Tiny Vector Matrix Library
 * Dense Vector Matrix Libary of Tiny size using Expression Templates
 *
 * Copyright (C) 2001 - 2003 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: CommaInitializer.h,v 1.14 2005/03/02 12:14:22 opetzold Exp $
 */

#ifndef TVMET_COMMA_INITIALIZER_H
#define TVMET_COMMA_INITIALIZER_H

#include <tvmet/CompileTimeError.h>

namespace tvmet {


/**
 * \class CommaInitializer CommaInitializer.h "tvmet/CommaInitializer.h"
 * \brief Initialize classes using a comma separated lists.
 *
 * The comma operator is called when it appears next to an object of
 * the type the comma is defined for. However, "operator," is not called
 * for function argument lists, only for objects that are out in the open,
 * separated by commas (Thinking C++
 * <a href=http://www.ida.liu.se/~TDDA14/online/v1ticpp/Chapter12.html>
 * Ch.12: Operator comma</a>).
 *
 * This implementation uses the same technique as described in Todd Veldhuizen
 * Techniques for Scientific C++
 * <a href=http://extreme.indiana.edu/~tveldhui/papers/techniques/techniques01.html#l43>
 * chapter 1.11 Comma overloading</a>.
 *
 * The initializer list is avaible after instanciation of the object,
 * therefore use it like:
 * \code
 * vector3d t;
 * t = 1.0, 2.0, 3.0;
 * \endcode
 * It's evaluated to (((t = 1.0), 2.0), 3.0)
 *
 * For matrizes the initilization is done row wise.
 *
 * If the comma separted list of values longer then the size of the vector
 * or matrix a compile time error will occour. Otherwise the pending values
 * will be written random into the memory.
 *
 */
template<class Obj, std::size_t LEN>
class CommaInitializer
{
  CommaInitializer();
  CommaInitializer& operator=(const CommaInitializer&);

private:
  /**
   * \class Initializer
   * \brief Helper fo recursive overloaded comma operator.
   */
  template<class T, std::size_t N> class Initializer
  {
    Initializer();
    Initializer& operator=(const Initializer&);

  public:
    typedef T						value_type;
    typedef T*						iterator;

  public:
    Initializer(iterator iter) : m_iter(iter) { }

    /** Overloads the comma operator for recursive assign values from comma
	separated list. */
    Initializer<value_type, N+1> operator,(value_type rhs)
    {
      TVMET_CT_CONDITION(N < LEN, CommaInitializerList_is_too_long)
      *m_iter = rhs;
      return Initializer<value_type, N+1>(m_iter + 1);
    }

  private:
    iterator 						m_iter;
  };

public:
  typedef typename Obj::value_type 			value_type;
  typedef value_type*					iterator;

public:
  CommaInitializer(const CommaInitializer& rhs)
    : m_object(rhs.m_object),
      m_data(rhs.m_data),
      m_wipeout_on_destruct(true)
  {
    rhs.disable();
  }

  /** Constructor used by Vector or Matrix operator(value_type rhs) */
  CommaInitializer(Obj& obj, value_type x)
    : m_object(obj),
      m_data(x),
      m_wipeout_on_destruct(true)
  { }

  /** Destructs and assigns the comma separated value. */
  ~CommaInitializer() {
    if(m_wipeout_on_destruct) m_object.assign_value(m_data);
  }

  /** Overloaded comma operator, called only once for the first occoured comma. This
      means the first value is assigned by %operator=() and the 2nd value after the
      comma. Therfore we call the %Initializer::operator,() for the list starting
      after the 2nd. */
  Initializer<value_type, 2> operator,(value_type rhs);

  void disable() const { m_wipeout_on_destruct = false; }

private:
  Obj& 							m_object;
  value_type 						m_data;
  mutable bool 						m_wipeout_on_destruct;
};


/*
 * Implementation
 */
template<class Obj, std::size_t LEN>
typename CommaInitializer<Obj, LEN>::template Initializer<typename Obj::value_type, 2>
CommaInitializer<Obj, LEN>::operator,(typename Obj::value_type rhs)
{
  m_wipeout_on_destruct = false;
  iterator iter1 = m_object.data();
  *iter1         = m_data;
  iterator iter2 = iter1 + 1;
  *iter2         = rhs;
  return Initializer<value_type, 2>(iter2 + 1);
}



} // namespace tvmet


#endif //  TVMET_COMMA_INITIALIZER_H

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