Re: Why use struct instead of class while using functors?
michael.lesniak@gmail.com wrote:
Hello,
I'm learning C++ for a couple of days and play a bit with the
algorithms provided in the STL. One thing I don't understand is the
fact that classes inherited of functors have to be defined using
structs.
They do not.
The code
template<class type> struct Print : public unary_function<type, void> {
void operator()(type& x) {
cout << x << endl;
}
};
in conjunction with
for_each(children.begin(), children.end(), Print<Node<type>*>());
does only work with struct but not with class, i.e.
template<class type> class Print : public unary_function<type, void> {
leads to a compiler error. I thought that classes and structs are more
or less equal, esp. since unary_function is a class itself, so why
can't I just inherit of it?
You can. struct and class is equivalent except for accessibility. The
problem most likely is that you forgot to make your operator() public.
Thanks for explanations,
Michael
/Peter
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