24.3.2 describes struct iterator, which didn't exist in the original HP STL implementation (the language wasn't rich enough at the time). For backwards compatibility, base classes are provided which declare the same nested typedefs:

24.3.4 describes iterator operation distance, which takes two iterators and returns a result. It is extended by another signature which takes two iterators and a reference to a result. The result is modified, and the function returns nothing.