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topological-sort DAG PREDprocedure

Sorts the directed acyclic graph dag DAG so that for every edge from vertex u to v, u will come before v in the resulting list of vertices.

DAG is a list of sublists. The car of each sublist is a vertex. The cdr is the adjacency list of that vertex, i.e. a list of all vertices to which there exists an edge from the car vertex. pred is procedure of two arguments that should compare vertices for equality.

Time complexity: O (|V| + |E|)

       '((shirt tie belt)
         (tie jacket)
         (belt jacket)
         (pants shoes belt)
         (undershorts pants shoes)
         (socks shoes))


(socks undershorts pants shoes watch shirt belt tie jacket)

If a cycle is detected during the sorting process, an exception of the condition kinds (exn runtime cycle) is thrown.