Re: [boost] reorder_iterator : iterator_adaptor

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2001-11-27 07:24:25

>>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 ?)

> 
> 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).

toon