Documentation

See: https://en.wikipedia.org/wiki/Topological_sorting. This function errors if edges mention nodes not mentioned in the node list or if the given graph contains cycles.

Same as `reverse (topSort nodes edges)` if alternative representations are considered the same. That is, topSort might produce multiple answers and still deliver on its promise of yielding a topologically sorted node list. Likewise, this function promises one of those lists in reverse, but not necessarily the reverse of topSort itself.