`module Avl_topo: ``sig end`

Topological sort of a graph.

Let *G* be a graph whose nodes are *x _{1}, ..., x_{n}*. Sorting

The client must provide an implementation of graph which fullfills the signature

`GRAPH`

.`module type GRAPH = ``sig end`

`module Make: ``functor (X : GRAPH) -> sig end`