Re: [boost] reorder_iterator : iterator_adaptor

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-11-27 07:44:02

----- Original Message -----
From: "Toon Knapen" <toon.knapen_at_[hidden]>

>
> >>So I guess we converge to the scheme were the Base is the actual random
> >>iterator and which is the second argument to the
> >>make_permutation_iterator such that the past-the-end can be specified by
> >>means of the first argument
> >>
> >
> > I don't see why the argument order to the generator(s) is important, but
> > yes, I always thought that past-the-end should be determined by a
position
> > in the sequence of permutation indices.
>
>
> If the order is the first argument you can easily specify the
> past-the-end iterator like :
>
> permutation_type end = make_permutation_iterator< sequence::iterator,
> sequence::iterator >( order.end() );
>
> OK, the notation is not optimal ;-). The idea is just that ultimatly the
> user would only need to create a past-the-end permutation iterator with
> one argument, the past-the-end of the order. This is simpler for the
> user and less confusing, since otherwise the user needs to construct the
> past-the-end from two iterator of which one is actually not used (and
> thus what value should it have ideally ?)

OK. Downside: all end-of-sequence iterators using the same permutation but a
different element set look identical, thwarting bug detection somewhat.

> > FWIW, still think "permutation iterator" is still a better name for this
> > beast, even though it can be used to do other kinds of shuffled
traversals.
>
> I agree. It should be stated clearly though that the
> permutation_iterator is not limited to bijections (every element in the
> original list maps to _exactly_ _one_ in the resulting permutation).

Yep. I suggest you make a new submission along the lines of Jens' recent
generator iterator adaptor. I'll be happy to add it to the library.

-Dave