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C++ Expression Templates

March 2003/C++ Expression Templates

Listing 1: Source code for object-oriented technique

class AbstractExpr {
   virtual double eval() const = 0;

class TerminalExpr : public AbstractExpr {

class NonTerminalExpr : public AbstractExpr {

class Literal : public TerminalExpr {
   Literal(double v) : _val(v) {}
   double eval() const { return _val; }
   const double _val;

class Variable : public TerminalExpr  {
   Variable(double& v) : _val(v) {}
   double eval() const { return _val; }
   double& _val;

class BinaryExpr : public NonTerminalExpr {
   BinaryExpr(const AbstractExpr* e1, const AbstractExpr* e2) 
     : _expr1(e1),_expr2(e2) {}
   virtual ~BinaryExpr () 
   { delete const_cast<AbstractExpr*>(_expr1); 
     delete const_cast<AbstractExpr*>(_expr2); 
   const AbstractExpr* _expr1;
   const AbstractExpr* _expr2;

class Sum : public BinaryExpr {
   Sum(const AbstractExpr* e1, const AbstractExpr* e2) 
     : BinExpr(e1,e2) {}
   double eval() const 
   { return _expr1->eval() + _expr2->eval(); }

— End of Listing —

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