March 01, 2003
C++ Expression Templates
March 2003/C++ Expression Templates
Listing 1: Source code for object-oriented technique
class AbstractExpr {
public:
virtual double eval() const = 0;
};
class TerminalExpr : public AbstractExpr {
};
class NonTerminalExpr : public AbstractExpr {
};
class Literal : public TerminalExpr {
public:
Literal(double v) : _val(v) {}
double eval() const { return _val; }
private:
const double _val;
};
class Variable : public TerminalExpr {
public:
Variable(double& v) : _val(v) {}
double eval() const { return _val; }
private:
double& _val;
};
class BinaryExpr : public NonTerminalExpr {
protected:
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 {
public:
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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