Re: [boost] [gacap]Is any interesting to "Generating All Combinations and Permutations"？

From: Jens Seidel (jensseidel_at_[hidden])
Date: 2007-11-13 05:46:07

On Tue, Nov 13, 2007 at 04:33:51PM +0800, Ben Bear wrote:
> 2007/11/13, Hervé Brönnimann <hervebronnimann_at_[hidden]>:
> > coherent interfaces.  Please look at:
> >
> > http://photon.poly.edu/~hbr/boost/combinations.html
> 
> I'll read this proposal.  It's a little long for me.

I did so already and found two minor issue:

To get all (n,r) combinations I have to specify r as value "middle".
According to the document it is possible to specify r=0 but not r=n?
("Without repetitions, r is specified by a middle position in the input
range [first, last) which is r positions away from first.") If r=n is
possible, middle=last would be a valid choice ==> [first, last)=>[first,
last].

I also do not understand
"Permutations and combinations can be ordered lexicographically,
starting with the subset at the first k positions of the sorted total
range, and ending with the subset at the last k positions of the same
range. Thus the effects of the algorithms are completely and
unambiguously defined."

What can be sorted? The elements of each r-tuple or do you want to say
that all determined permutations and combinations are sorted (provided
in a special order)?

Probably you want to use r instead of k in the text above? I first
thougth that I can get all values in a single r-tuple unsorted by
specifying a parameter k=0 and wondered that it affects the beginning
and end of some data.

Could you please try to improve it a little bit? Maybe by giving some
examples in the documentation?

Thanks,
Jens