C++ named requirements:LegacyForwardIterator
A LegacyForwardIterator is a LegacyIterator that can read data from the pointed-to element.
A LegacyForwardIterator is a LegacyIterator that can read data from the pointed-to element.
A LegacyForwardIterator is a LegacyIterator that can read data from the pointed-to element.