Add a toMap function to unwrap a Graph (#18)

Author: notquiteamonad

CHANGELOG.md

@@ -19,6 +19,7 @@ Breaking changes:
 
 New features:
 - Added `Foldable` and `Traversable` instances for `Graph` (#16 by @MaybeJustJames)
+- Added `toMap` to unwrap `Graph` (#18)
 
 Bugfixes:
 

src/Data/Graph.purs

@@ -4,6 +4,7 @@ module Data.Graph
   ( Graph
   , unfoldGraph
   , fromMap
+  , toMap
   , vertices
   , lookup
   , outEdges
@@ -62,6 +63,11 @@ unfoldGraph ks label edges =
 fromMap :: forall k v. Map k (Tuple v (List k)) -> Graph k v
 fromMap = Graph
 
+-- | Create a `Map` which maps vertices to their labels and
+-- | outgoing edges from a `Graph`.
+toMap :: forall k v. Graph k v -> Map k (Tuple v (List k))
+toMap (Graph g) = g
+
 -- | List all vertices in a graph.
 vertices :: forall k v. Graph k v -> List v
 vertices (Graph g) = map fst (M.values g)