[boost] Re: Re: Re: Re: String Algo Review Results

From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2003-11-03 05:09:34

"Pavol Droba" <droba_at_[hidden]> wrote in message
news:20031103095123.GA12977_at_lenin.felcer.sk...
> On Mon, Nov 03, 2003 at 08:14:36PM +1100, Thorsten Ottosen wrote:
>
> [snip]
> > > Actualy, it is not fully correct. 'iterator_range' is realy intended
to
> > > work with
> > > iterators only. Along with the operations you have specified, it has
> > > a set of typedefs and operations are implemented using iterator
> > > operations.
> > >
> > I assume you mean
> >
> >  typedef iterator_range< IteratorT >
type;
> > // this type
> >   typedef boost::detail::iterator_traits< IteratorT >::value_type
> > value_type;       // Encapsulated value type.
> >   typedef boost::detail::iterator_traits< IteratorT >::reference
> > reference;        // Reference type.
> >   typedef boost::detail::iterator_traits< IteratorT >::difference_type
> > difference_type;  // Difference type.
> >   typedef boost::detail::iterator_traits< IteratorT >::difference_type
> > size_type;        // Size type.
> >   typedef IteratorT
> > const_iterator;   // const_iterator type
> >   typedef IteratorT
> >
> > AFAICT, the could be replaced by a single typedef 'value_type' and then
you
> > can let the container traits
> > take care of the rest. This would also be good for compilation times.
>
>
> I don't know, how container traits could do all this. At least iterator
and const_iterator
> typedef must be present and this strongly implies iterator afinity.

It can easily be done by specializing iterator taits as for std::pair.

> > About the operations, then size() should be the only one who need
special
> > treatment. About
> >   1.. void reverse() ;Reverse the range.
> >
> >   Reverse the range, i.e. swap begin and end
> >
> > then I don't see why this should be. AFAICT, the class's invariant
should be
> >
> > 'end' is reachable from 'begin' (or begin < end ).
> >
> > If that is not the case, then we could get wierd results (so I really
don't
> > get this). OTOH, if the class has no invariant, we might as well use
> > std::pair.
>
> Sure, we can use std::pair. iterator_range is not supposed to add much
more. Only I find
> it a way more clean an easier to use, because, you need to specify only
one template argument
> (unlike in confusing pair) and the name denotes what is the semantic value
of the contained
> pair of iterators.

Please tell me what the invariant of iterator_range is suposed to be and
then justify why
reverse() don't break it. If it does, the operation does not make sense, and
then there seem to be no
reason why this could not be a generic range.

> Adding additional functionality and meaning to the iterator_range will
break its original
> purpose.

so far we don't know what the purpose is.

-Thorsten