(Partially) specializing a non-type template parameter of dependent type

by

See paragraph [temp.class.spec] 14.5.5/8 of the standard:

The type of a template parameter corresponding to a specialized
non-type argument shall not be dependent on a parameter of the
specialization. [ Example:

template <class T, T t> struct C {};
template <class T> struct C<T, 1>; // error

template< int X, int (*array_ptr)[X] > class A {};
int array[5];
template< int X > class A<X,&array> { }; // error

—end example ]

The answer to your edit: the easiest workaround is to replace a non-type template parameter with a type one:

#include <type_traits>

template <typename T, typename U>
struct X_;

template <typename T, T N>
struct X_<T, std::integral_constant<T, N>> {};

template <typename T>
struct X_<T, std::integral_constant<T, 0>> {};

template <typename T, T N>
struct X : X_<T, std::integral_constant<T, N>> {};

More Related Contents:

  1. C++ function template partial specialization?
  2. “invalid use of incomplete type” error with partial template specialization
  3. Partial specialization of function templates
  4. Why can templates only be implemented in the header file?
  5. What are some uses of template template parameters?
  6. Difference of keywords ‘typename’ and ‘class’ in templates?
  7. C++ templates that accept only certain types
  8. Function passed as template argument
  9. Is it possible to emulate template?
  10. Can standard container templates be instantiated with incomplete types?
  11. static_assert dependent on non-type template parameter (different behavior on gcc and clang)
  12. How to initialize std::array elegantly if T is not default constructible?
  13. Why should I avoid std::enable_if in function signatures
  14. Template tuple – calling a function on each element
  15. C++ templates, undefined reference
  16. Are C++ Templates just Macros in disguise?
  17. Restrict C++ Template Parameter to Subclass
  18. C++ template functions overload resolution
  19. Why is the keyword “typename” needed before qualified dependent names, and not before qualified independent names?
  20. “Undefined symbols” linker error with simple template class
  21. Two phase name lookup for C++ templates – Why?
  22. using class name in a class template without template parameters
  23. Template instantiation details of GCC and MS compilers
  24. How can I expand call to variadic template base classes?
  25. Template Metaprogramming – Difference Between Using Enum Hack and Static Const
  26. Dependent name resolution & namespace std / Standard Library
  27. How to typedef a template class? [duplicate]
  28. C++ template function compiles in header but not implementation
  29. Conditional compilation based on template values?
  30. How to test whether class B is derived from template family of classes

Leave a Comment