C++ Expression Templates
By Angelika Langer and Klaus Kreft, March 01, 2003
Do you want high-performance, readable expressions? Expression templates do it all.
March 2003/C++ Expression Templates
Listing 10: The modified classes and their use for calculating the Gauss distribution
class Literal {
public: Literal(double v) : _val(v) {}
double eval(double) const { return _val; }
private: const double _val;
};
class Identity {
public: double eval(double d) const { return d; }
};
template <class ExprT1,class ExprT2, class BinOp>
class BinExpr {
public: double eval(double d) const
{ return _op(_expr1.eval(d),_expr2.eval(d)); }
};
...
template <class ExprT1,class ExprT2, class BinOp>
class BinaryExpr {
public:
BinaryExpr(ExprT1 e1, ExprT2 e2,BinOp op=BinOp())
: _expr1(e1),_expr2(e2),_op(op) {}
double eval() const
{ return _op(_expr1.eval(),_expr2.eval()); }
private:
exprTraits<ExprT1>::expr_type _expr1;
exprTraits<ExprT2>::expr_type _expr2;
BinOp _op;
};
— End of Listing —
