title: Does pair.first return a reference to the first value?
body: <p>In the C++ standard library, there is an object called the pair. Pair.first and Pair.second return the first and second values of the pair object, respectively. I want to increment the first value by one under a conditional (my pair is a pair). It's throwing "needs 1-value" when I try to do this. This could be because somewhere along the way I am not passing in a value by reference, but it could also be that .first does not return the first value of the pair by reference.
  Does anyone know if it does?</p>