algorithm for sorting functional expressions

[Marc 'BlackJack' Rintsch]

In <1165215032.749560.171530 at 16g2000cwy.googlegroups.com>, chrisguest
wrote:

> So I suspect that this is a common problem for those familiar with
> partially ordered sets or directed graphs. I'm wondering if anyone else
> is familiar with this problem and knows an efficient algorithm that
> will solve it. It would be good if any such algorithm would be able to
> check for circular definitions in the input.

You are looking for "topological sort".  Feed a search engine with that
term.  :-)

Ciao,
	Marc 'BlackJack' Rintsch