literalexpr.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: LiteralExpr

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

#include <functional> // required for base classes

/****************************************************************************
 * LiteralExpr represents a literal which appears in the expression.
 */

   template <class argT, class resT = argT>
   class LiteralExpr : public std::unary_function<argT, resT>
   {
      public:
         typedef std::unary_function<argT, resT>::argument_type argument_type;
         typedef std::unary_function<argT, resT>::result_type result_type;

      private:
         resT value;

      public:

         // Default constructor
         LiteralExpr() : value( resT() ) { }

         // Conversion constructor
         explicit LiteralExpr(const argument_type& v) : value(v) { }

         // Copy Constructor
         LiteralExpr(const LiteralExpr& aLiteralExpr) : value(aLiteralExpr.value) {}

  	      //Assignment Operator
         LiteralExpr& operator= (const LiteralExpr& aLiteralExpr)
         {
            if(&aLiteralExpr != this)
               value = aLiteralExpr.value;
            return *this;
         }

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

         // Destructor
         ~LiteralExpr() {}

   };

#endif