Understanding C++ Expression Templates - Angelika Langer

15A Simplified OO ImplementationEliminate the representation of the composite and the leafobject as data members.! Instead of passing information to the constructor andmemorizing them for subsequent evaluation,! pass them to the directly to the evaluation function.SimpleDotProduct (T* a, T* b) :v1(a), v2(b) {}virtual T eval() { return (*v1)*(*v2); }becomesT eval(T* a, T* b, size_t dim) { return (*a)*(*b); }© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(29)last update: 11/7/2005 ,21:37A Simplified OO Implementationtemplate class CompositeDotProduct : public DotProduct {public:virtual T eval(T* a, T* b, size_t dim){ return SimpleDotProduct().eval(a,b,dim)+ ((dim==1) ? 0: CompositeDotProduct().eval(a+1,b+1,dim-1));}};template class SimpleDotProduct : public DotProduct {public:virtual T eval(T* a, T* b, size_t dim){ return (*a)*(*b); }};© Copyright 1995-2000 by Angelika Langer. All Rights Reserved.http://www.AngelikaLanger.com(30)last update: 11/7/2005 ,21:37