Why use initializer_list instead of vector in parameters?

Question

What is the actual benefit and purpose of initializer_list, for unknown number of parameters? Why not just use vector and be done with it?

In f

Answer 1

Well, std::vector has to use initializer_list to get that syntax as it obviously can't use itself.

Anyway, initializer_list is intended to be extremely lightweight. It can use an optimal storage location and prevent unnecessary copies. With vector, you're always going to get a heap allocation and have a good chance of getting more copies/moves than you want.

Also, the syntax has obvious differences. One such thing is template type deduction:

struct foo {
    template  
    foo(std::initializer_list) {}
};

foo x{1,2,3}; // works

vector wouldn't work here.