how copy the first elements of pair in vector to another vector?

Question

I have a std::vector with element of the type std::pair. With some algorithm, I return two iterators (range) so I would like to pick up all elements within that range and copy t

Answer 1

It's because of the operator precedence. The select operator . has higher precedence than the dereference operator *.

So what the compiler thinks you're writing is

*(it1.first)

when you mean

(*it1).first