17 Templates [temp]

17.5 Template declarations [temp.decls]

17.5.1 Class templates [temp.class] Member functions of class templates [temp.mem.func]

A member function of a class template may be defined outside of the class template definition in which it is declared. [Example:

template<class T> class Array {
  T* v;
  int sz;
  explicit Array(int);
  T& operator[](int);
  T& elem(int i) { return v[i]; }

declares three function templates. The subscript function might be defined like this:

template<class T> T& Array<T>::operator[](int i) {
  if (i<0 || sz<=i) error("Array: range error");
  return v[i];

end example]

The template-arguments for a member function of a class template are determined by the template-arguments of the type of the object for which the member function is called. [Example: The template-argument for Array<T>​::​operator[]() will be determined by the Array to which the subscripting operation is applied.

Array<int> v1(20);
Array<dcomplex> v2(30);

v1[3] = 7;                      // Array<int>​::​operator[]()
v2[3] = dcomplex(7,8);          // Array<dcomplex>​::​operator[]()

end example]