Define emap in terms of bimap where available

snowleopard · Jan 23, 2019 · bd0043a · bd0043a
1 parent baeafb9
commit bd0043a
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/src/Algebra/Graph/Labelled.hs b/src/Algebra/Graph/Labelled.hs
@@ -490,7 +490,12 @@ transpose = foldg empty vertex (fmap flip connect)
 -- emap g . emap h        == emap (g . h)
 -- @
 emap :: (e -> f) -> Graph e a -> Graph f a
-emap f = foldg Empty Vertex (Connect . f)
+emap f =
+#if MIN_VERSION_base(4,8,0)
+  first f
+#else
+  foldg Empty Vertex (Connect . f)
+#endif
 
 -- | Construct the /induced subgraph/ of a given graph by removing the
 -- vertices that do not satisfy a given predicate.