Template function pointer

Question

Suppose we have the general function pointer:

template <class ArgT, class RetT, class F>
struct A {
    F f;
public:
    A(F f) : f(f) {}

    RetT operator()(ArgT arg) { return f(arg); }
};

Why does this work?

template <class ArgT, class RetT, class F>
class B {
    A<ArgT, RetT, F> test;
};

... and this not ?

class C {
    template <class ArgT, class RetT, class F>
    A<ArgT, RetT, F> test;
};

error C3857: 'C::test': multiple template parameter lists are not allowed

I need to define a class like in last example (class C), how can I do that?

because it doesn't make sense. how can you use it and how can compile generate code for it? — Bryan Chen
– Bryan Chen, Commented Jan 2, 2015 at 10:33

m.elahi · Accepted Answer · 2015-01-03 08:11:12Z

1

Because variables can't have template. In fact just classes and functions can have template.

Edit: As Alan Stokes said, in C++14, variables also can have template.

answered Jan 2, 2015 at 10:34

m.elahi

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