That is very interesting, thanks.
(As you know, I am using your module combinatorics.nim in [https://github.com/StefanSalewski/nim-gi2](https://github.com/StefanSalewski/nim-gi2). Would be nice if that module would be put into Nim's standard lib -- it works fine, but I have never tried to understand it yet, I guess it is not trivial...)
