Map Iterator working for begin() but not for rbegin()

Question

I have some class called Order. For some reason, the following code won't compile while using rbegin(), but it works for begin(). Is there a problem in the way I'm declaring the iterator or perhaps a problem with my pointer reference?

map<double, list<Order*>> m
typedef map<double, list<Order*>>::iterator iter;
iter iterator;

iterator = m.rbegin(); // this only works for m.begin()

Thank you!

Answer 1

rbegin()返回一个reverse_iterator ，而不是一个iterator 。

Answer 2

The types returned from begin() and rbegin() are different:

• begin() returns std::map<K, V>::iterator
• rbegin() returns std::reverse_iterator<std::map<K, V>::iterator>