Мобильная версия(Note: This question is about not having to specify the number of elements and still allow nested types to be directly initialized.)
This question discusses the uses left for a C array like int arr[20];. On his answer, @James Kanze shows one of the last strongholds of C arrays, it's unique initialization characteristics:
int arr[] = { 1, 3, 3, 7, 0, 4, 2, 0, 3, 1, 4, 1, 5, 9 }; We don't have to specify the number of elements, hooray! Now iterate over it with the C++11 functions std::begin and std::end from (or your own variants) and you never need to even think of its size.
Now, are there any (possibly TMP) ways to achieve the same with std::array? Use of macros allowed to make it look nicer.
??? std_array = { "here", "be", "elements" }; Edit: Intermediate version, compiled from various answers, looks like this:
#include #include template std::array make_array(T&& head, Tail&&... values) { return { std::forward(head), std::forward(values)... }; } // in code auto std_array = make_array(1,2,3,4,5); And employs all kind of cool C++11 stuff:
- Variadic Templates
- sizeof...
- rvalue references
- perfect forwarding
- std::array, of course
- uniform initialization
- omitting the return type with uniform initialization
- type inference (auto)
And an example can be found here.
However, as @Johannes points out in the comment on @Xaade's answer, you can't initialize nested types with such a function. Example:
struct A{ int a; int b; }; // C syntax A arr[] = { {1,2}, {3,4} }; // using std::array ??? std_array = { {1,2}, {3,4} }; Also, the number of initializers is limited to the number of function and template arguments supported by the implementation.
Источник: https://stackoverflow.com/questions/611 ... 3-behaviou
