Re: [boost] [bimap][multi_index][range] sub_range vs std::pair<iter, iter>

From: Matias Capeletto (matias.capeletto_at_[hidden])
Date: 2007-05-23 18:26:29

On 5/23/07, "JOAQUIN LOPEZ MU?Z" <joaquin_at_[hidden]> wrote:
> ----- Mensaje original -----

> > 1) Do you think that the range functions should return a
> > sub_range<map_type>instead of a std::pair<iter,iter>?
> [...]
>
> IMHO, no, so as to avoid unasked for dependencies between
> libraries --both at a conceptual and #include level.

Lets see what Thorsten have to said about this.
IMO in this case the dependency will not heart anybody.
Looking at this code:

map_type::sub_range r = m.range(...,...);
for( map_type::iterator i = r.begin(), iend = r.end(); i != iend; ++i)
{
   ....
}

It is IMO easier to explain than:

map_type::sub_range r = m.range(...,...);
for( map_type::iterator i = r.first, iend = r.second; i != iend; ++i)
{
   ....
}

But I have to admit that if Boost.Range framework is used both
examples are equal:

map_type::sub_range r = m.range(...,...);
for( map_type::iterator i = begin(r), iend = end(r); i != iend; ++i)
{
   ....
}

> Moreover, one can always convert the std::pair to a range
> very easily, although this conversion would be much
> simpler if iterator_range and sub_range provided ctors
> taking std::pairs of iterators --Thorsten, would you
> consider adding this a good idea?

They are already provided. I have just being playing with them with Boost.Bimap.

> > 2) In any case do you think that including typedef for the returned
> > range type will make code more readable?
> > The idea is to define:
> >
> > typedef -range_type- sub_range; // the name can be different
> > typedef -const_range_type- const_sub_range;
> >
> > So the user code will look like this:
> >
> > typedef bimap<string,int> bm_type;
> > bm_type bm;
> > //...
> > bm_type::left_sub_range r = bm.left.range(...,...);
>
> I am not sure. On one hand, the syntax above is obviously
> more concise, but on the other hand a casual reader would
> have to look up what sub_range is to fully understand the
> code, whereas the std::pair is self explanatory and moreover
> it's honored by the tradition of equal_range().

At least for Boost.Bimap, compare:

std::pair<
    bm_type::map_by<name>::const_iterator,
    bm_type::map_by<name>::const_iterator

> r = bm.by<name>().range(...,....);

with:

bm_type::map_by<name>::const_sub_range r = bm.by<name>().range(...,....);

Maybe "sub_range" is not the better word. IMO it is not a bad election.

Best regards
Matias