Partial class template argument deduction in C++17

by

CTAD (Class Template Argument Deduction) is an all or nothing process currently. You either specify nothing and allow the compiler to deduce all of the arguments, or you specify all of the arguments taking the compiler out of the loop.

There is a paper (P1021R0) which asks for this and more, but it has not yet been accepted. There was a paper asking for partial specialization but after revisions it has been removed. The newest revision still includes a proposal to have CTAD function when using an alias.

Per @Barry Support for Alias templates (P1814) and Aggregates (P1816) have been added to the working draft for C++20. No support for partial CTAD or CTAD with inherited constructors has been added.

More Related Contents:

  1. What are template deduction guides and when should we use them?
  2. Variadic deduction guide not taken by g++, taken by clang++ – who is correct?
  3. Deduction guides and variadic class templates with variadic template constructors – mismatched argument pack lengths
  4. what is the concept of evaluation of expression z = (y = 30) + (y = 10) + (y = 20); [closed]
  5. What are Aggregates and PODs and how/why are they special?
  6. What are the evaluation order guarantees introduced by C++17?
  7. Deprecated header replacement
  8. experimental::filesystem linker error
  9. Understanding std::hardware_destructive_interference_size and std::hardware_constructive_interference_size
  10. Is stateful metaprogramming ill-formed (yet)?
  11. What is string_view?
  12. std::lock_guard or std::scoped_lock?
  13. Is a pointer with the right address and type still always a valid pointer since C++17?
  14. C++17 class template partial deduction
  15. Lambda implicit capture fails with variable declared from structured binding
  16. Try to understand compiler error message: default member initializer required before the end of its enclosing class
  17. structured bindings: when something looks like a reference and behaves similarly to a reference, but it’s not a reference
  18. “If constexpr” in C++17 does not work in a non-templated function
  19. polymorphic_allocator: when and why should I use it?
  20. Multiple SFINAE class template specialisations using void_t
  21. Why void_t doesnt work in SFINAE but enable_if does
  22. How to enable C++17 support in VSCode C++ Extension
  23. “constexpr if” vs “if” with optimizations – why is “constexpr” needed?
  24. What are use cases for structured bindings?
  25. How similar are Boost.Filesystem and the C++ standard filesystem library?
  26. Do I need to put constexpr after else-if?
  27. Constexpr if alternative
  28. Will I be able to declare a constexpr lambda inside a template parameter?
  29. Avoiding extra move in make_unique/make_shared/emplace/etc for structures that use aggregate initialization
  30. Directly write into char* buffer of std::string

Leave a Comment