[boost] [Range] initial feedback on return values of algorithms

From: Thorsten Ottosen (tottosen_at_[hidden])
Date: 2006-02-02 09:46:31

Dear all,

The plan is to include range-based overloads of std algorithms in the 
next boost.range.

We have several options for specifying the return type
of functions that normally return an iterator that I would like your 
feedback on.

1. leave the return type as it is.

2. return an iterator_range describing the range [found,end)
this allows us to do stuff like

    namespace br = boost::ranges;
    br::erase( rng, br::unique(rng) );

3. inspired by John Torjo's range lib, provide a whole list of possible 
   return values:

        std::vector<int> v;
        namespace br = boost::ranges;
        br::unique(v);
        br::unique<br::return_found>(v);
        br::unique<br::return_next>(v);
        br::unique<br::return_prior>(v);
        br::unique<br::return_begin_found>(v);
        br::unique<br::return_begin_next>(v);
        br::unique<br::return_begin_prior>(v);
        br::unique<br::return_found_end>(v);
        br::unique<br::return_next_end>(v);
        br::unique<br::return_prior_end>(v);

the default would be the range [found,end), but the you can pick
different slices or simply iterators. In the above scheme, "found" is 
the iterator normally returnes by the algorithm, "next" means 
boost::next(found) and "prior" means boost::prior(found).

The advantage of the latter approach is

- flexibility/power
- safety (we can tjeck that next(found) and prior(found) stays in range)

The disadvantage is that it will require twice as many overloads in 
C++03 (since we can't put defaults template arguments in function 
templates).

Any opinions?

-Thorsten