Add unsnoc function.

CHANGES.md

@@ -11,6 +11,7 @@
 * Hides all Show class functions. Only the Class itself is exported. Forbids
 * custom instances that are not GHC derived.
 * Export`` encodeUtf8`` and ``decodeUtf8`` functions by default.
+* Adds ``unsnoc`` function.
 
 0.1.5
 =====

src/Protolude.hs

@@ -12,6 +12,7 @@ module Protolude (
   map,
   (&),
   uncons,
+  unsnoc,
   applyN,
   print,
   show,
@@ -362,6 +363,13 @@ uncons :: [a] -> Maybe (a, [a])
 uncons []     = Nothing
 uncons (x:xs) = Just (x, xs)
 
+unsnoc :: [x] -> Maybe ([x],x)
+unsnoc = foldr go Nothing
+  where
+    go x mxs = Just (case mxs of
+       Nothing -> ([], x)
+       Just (xs, e) -> (x:xs, e))
+
 applyN :: Int -> (a -> a) -> a -> a
 applyN n f = X.foldr (.) identity (X.replicate n f)