How does the range-based for work for plain arrays?

Question

In C++11 you can use a range-based for, which acts as the foreach of other languages. It works even with plain C arrays:

int number         


        

Answer 1

I think that the most important part of this question is, how C++ knows what the size of an array is (at least I wanted to know it when I found this question).

C++ knows the size of an array, because it's a part of the array's definition - it's the type of the variable. A compiler has to know the type.

Since C++11 std::extent can be used to obtain the size of an array:

int size1{ std::extent< char[5] >::value };
std::cout << "Array size: " << size1 << std::endl;

Of course, this doesn't make much sense, because you have to explicitly provide the size in the first line, which you then obtain in the second line. But you can also use decltype and then it gets more interesting:

char v[] { 'A', 'B', 'C', 'D' };
int size2{ std::extent< decltype(v) >::value };
std::cout << "Array size: " << size2 << std::endl;