模板参数C的差异 <void ()> 和C <void (*)()>

Question

I don't understand difference between template arguments

template <class T>
class C
{
   T t;
};

void foo()
{
   C<void ()> c1; //isn't compiled
   C<void (*)()> c2;
}

What is the type void ()? Such kind of types is used in boost::function..

Answer 1

void() is a function type. void(*)() is a pointer type. In C++ you cannot have variables of function type, so T t; doesn't compile when T is void() .

Answer 2

By

C<void ()> c1;
C<void (*)()> c2;

compiler expects you're passing pointer to a function signature. and first one is not a pointer.

Answer 3

第一个void（）是一个函数，而第二个void（*）（）是一个指向函数的指针。