template<class T> class Array { T* v; int sz; public: explicit Array(int); T& operator[](int); T& elem(int i) { return v[i]; } };The prefix template<class T> specifies that a template is being declared and that a type-name T may be used in the declaration.
template<class T1, class T2> struct A { void f1(); void f2(); }; template<class T2, class T1> void A<T2,T1>::f1() { } // OK template<class T2, class T1> void A<T1,T2>::f2() { } // error
template<class ... Types> struct B { void f3(); void f4(); }; template<class ... Types> void B<Types ...>::f3() { } // OK template<class ... Types> void B<Types>::f4() { } // error
template<class T> class Array { T* v; int sz; public: explicit Array(int); T& operator[](int); T& elem(int i) { return v[i]; } };
template<class T> T& Array<T>::operator[](int i) { if (i<0 || sz<=i) error("Array: range error"); return v[i]; }
template<class T> struct A { class B; }; A<int>::B* b1; // OK: requires A to be defined but not A::B template<class T> class A<T>::B { }; A<int>::B b2; // OK: requires A::B to be defined
template<class T> class X { static T s; }; template<class T> T X<T>::s = 0; struct limits { template<class T> static const T min; // declaration }; template<class T> const T limits::min = { }; // definition
template <class T> struct A { static int i[]; }; template <class T> int A<T>::i[4]; // 4 elements template <> int A<int>::i[] = { 1 }; // OK: 1 element