expr.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: Expr

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

#include <functional> // required for base classes

 /****************************************************************************
 * Expr is a wrapper class which contains a more interesting expression type,
 * such as IdentityExpr, LiteralExpr, or BinExpr.
 */

   template <class exprT>
   class Expr : public std::unary_function<exprT::argument_type, exprT::result_type>
   {
      public:
         typedef typename exprT expr_type;
         typedef typename exprT::argument_type argument_type;
         typedef typename exprT::result_type result_type;

      private:
         exprT expr;

      public:
         // Conversion constructor
         explicit Expr(const exprT & e) : expr(e) {;}

         //Default constructor
         Expr() : expr() {;}

	      //Copy constructor
         Expr(const Expr& anExpr ) : expr(anExpr.expr ) {}

	      //Operator=
         Expr& operator= (const Expr& anExpr)
         {
            if(&anExpr != this)  expr = anExpr.expr;
            return *this;
         }

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

         // Destructor
         ~ Expr() {}
   };

#endif