assignment

assignment/digraph.mli

@@ -0,0 +1,35 @@
+type t                              (* the abstract digraph type *)
+type edge = string * string * int   (* type of an edge *)
+
+(** raised by [add_edge] and [of_edges] when adding an edge to a digraph;
+    this could happen when the edge has non-positive length, or the 2 vertices
+    in the edge are not distinct, or the edge to add is a "duplicate" in the
+    sense that there is already an edge in the graph with the same source
+    and destination vertices, and which can be of the same length or of
+    different lengths.
+*)
+exception Invalid of string   (* the string argument specifies the reason *)
+
+(** [empty] is the empty digraph *)
+val empty : t
+
+(** [add_edge edge graph] adds [edge] to [graph].
+    Raises: [Inv_edge] if [edge] is invalid; raises [Inv_graph] if [edge] is
+            a duplicate with a different length *)
+val add_edge : edge -> t -> t
+
+(** [of_edges edges] is the digraph formed from the list [edges].
+    May raise [Inv_edge] or [Inv_graph] (see above) *)
+val of_edges : edge list -> t
+
+(** [edges graph] is the sorted list of all distinct edges in [graph] *)
+val edges : t -> edge list
+
+(** [vertices graph] is the list of all distinct vertices (in alphabetical
+    order) of [graph] *)
+val vertices : t -> string list
+
+(** [neighbors vertex graph] is the list of neighbors of [vertex] in
+    [graph]; each neighbor is a pair of the form ([vertex2], [length]) which
+    indicates there is an edge from [vertex] to [vetex2] of length [length]) *)
+val neighbors : string -> t -> (string * int) list