Difference between vector::begin() and std::begin()

Question

While iterating over a vector in c++, I noticed there is a begin() function in the standard library, and also a begin() as a member function of the vector class. What, if any, is the difference between the two, and which should be used over the other?

Example:

vector<int> numbers; //Code to put values in my vector for (vector<int>::iterator i = numbers.begin(); i < numbers.end(); i++)     cout << *i << '\n'; 

vs:

vector<int> numbers; //Code to put values in my vector for (vector<int>::iterator i = std::begin(numbers); i < std::end(numbers); i++)     cout << *i << '\n'; 

Answer 1

std::begin() was added in C++11 to make it easier to write generic code (e.g. in templates). The most obvious reason for it is that plain C-style arrays do not have methods, hence no .begin(). So you can use std::begin() with C-style arrays, as well as STL-style containers having their own begin() and end().

If you're writing code which is not a template, you can ignore std::begin(); your fellow programmers would probably find it odd if you suddenly started using it everywhere just because it's new.