To my knowledge, there is no ref keyword in C++.
In the D language ref is short for reference, and used for function parameters it's equivalent to a non-const reference declaration in C++.
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void f(ref int i); // D
void f(int &i); // C++
auto comes from good old C.
Up until C++11 it used to describe automatic variables. The complement of auto is static.
Now, all local variables are automatic by default, which is why the keyword was very seldom used -- which is why in C++11 its meaning changed to automatic type inference. If the compiler can infer the type of a variable from its initialization, you can use auto instead of writing the type yourself.
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std::vector<int>::const_iterator it1 = vi.begin(); // C++98
auto it2 = vi.cbegin(); // C++11
std::map<char, int> mci;
for (constauto &p: mci); // p is std::pair<char, int>
const... you use it to mark your variables constant. You also use it to mark your references constant. Finally, you use it to signify that a member function doesn't change the member data.
I can repeat the third time: there is no such keyword as ref in C++ This means that using such identifier is implementation defined. In the C++ Standard there is defined function ref(). But names of functions have nothing common with keywords except operator functions new and delete.