Question

I have a map object to which I want to insert a new element. After doing this, I want to make sure that this newly inserted element was inserted at the end. To do this, I have devised the following way:

map<T1,T2> m;
//populate m
auto ret_pair = m.insert({o1,o2}); //o1,o2 objects of types T1,T2

auto end = m.cend();
--end;
if (ret_pair.first != end) //<-- this worries me
  throw runtime_error("boom");

The line where I compare the two iterators worries me, because I’m not sure if I can rely on these different iterators to be the same, even if the point to the same thing.

What do you think? Why would this (not) work?

Answer 1

Iterators which point to the same element compare equal. If they didn’t, every algorithm in the standard library would break.

So yes, your code is fine.