Re: [boost] [ptr_map] iterator changes, feedback welcome

From: Sam Partington (sam.partington_at_[hidden])
Date: 2006-02-21 04:05:52

Thorsten Wrote :
> 1. AFIICT it is not possible to let operator->() return a tuple of
> references s.t. ->second would yeild T& instead of T*. Reason: the
> pointer might be null.

Well, you could throw a bad_pointer here, but....

> 2. Operator*() now returns a tuple [key,T*]; this is necessary because
> you may need access to both the key inside e.g predicates for
> algorithms. Operator->() also returns the same tuple, so that you can
> make the familiar loop in #1. The question is #1 is necessary/wanted
> given that it removes the current behavior where operator->() returns
> a T* s.t. you can more easily access the mapped object. Would it
> be preferable to keep operator-<() with a T* return type?

I think the important thing here is to provide a consistent behaviour.
 ptr_map is an extension to std::map, and so should behave like
std::map.

As Felipe says, any deviations from the interface of std::map will
make it harder to write generic code, and should be avoided where
possible.

I think it would be surprising to users if the following two
operations returned different types :

(*i).second
i->second

On a std::map they are the same, so I think they should be the same for ptr_map.

Sam