identityexpr.h

精确的函数表达模板,里面包含了许多C和C++的函数表达模板

/****************************************************************************
 * Copyright (C) 2001        Piece Wise Functions
 *                           Carlo Galotto
 *                           Italy
 *                           Email: [e-mail]
 *                                  [e-mail]
 *
 *
 * This framework is free  software; you can  redistribute it and/or modify
 * it. This framework 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.
 * The proposed framework is based upon the paper "Expression Templates" by
 * Todd Veldhuizen.
 ****************************************************************************/

// Class: IdentityExpr

#ifndef __IDNTTEXP_H  //Required for current class
  #define __IDNTTEXP_H

#include <functional> // required for base classes

/****************************************************************************
 * IdentityExpr is a placeholder for the variable in the expression.
 */
   template <class T>
   class IdentityExpr : public std::unary_function<T, T>
   {
      public:
         typedef std::unary_function<T, T>::argument_type argument_type;
         typedef std::unary_function<T, T>::result_type result_type;

      public:
         // Default constructor
         IdentityExpr() {}

         // Evaluator operator
         result_type operator()(const argument_type& x) const { return x; }

         // Destructor
         ~IdentityExpr() {}
   };

#endif