vector emplace_back usage (C++11) of containing another vector (partial vector)

Question

Has anyone known related reference for such emplace_back usage (C++11)?

void func(const vector <int>  &A){
    vector <vector <int> > B;
    B.emplace_back(A.cbegin() , A.cend());  // emplace vector A directly
}

Answer 1

You'd better searched them on Google or cppreference.com before asking for any further reference.

• For emplace_back(): http://en.cppreference.com/w/cpp/container/vector/emplace_back
• For cbegin()/cend() (since C++11): they are same with begin()/end() http://en.cppreference.com/w/cpp/container/vector/begin

Answer 2

I'm not sure what your real question is, but the code you have shown inserts a new vector in-place inside B. The new vector is initialized by calling its constructor (4) which takes the two arguments A.cbegin() , A.cend().

You can think of it as an optimized version of

B.push_back(std::vector<int>(A.cbegin() , A.cend()));