Define a foldr "safe" minimum

src/FoldableHelp.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE TupleSections #-}
 module FoldableHelp
     ( safeMinimumOn
+    , safeMinimumOnr
     , safeMinimumOnMaybe
     , module Data.Foldable
     )
@@ -21,6 +22,14 @@ safeMinimumOn f = foldl' g Nothing
         | f x < f y = Just x
         | otherwise = Just y
     g Nothing y = Just y
+safeMinimumOnr :: (Foldable t,Ord b) => (a -> b) -> t a -> Maybe a
+{-# INLINE safeMinimumOnr #-}
+safeMinimumOnr f = foldr g Nothing
+  where
+    g y (Just x)
+        | f x < f y = Just x
+        | otherwise = Just y
+    g y Nothing = Just y
 safeMinimumOnMaybe :: (Ord b) => (a -> Maybe b) -> [a] -> Maybe a
 safeMinimumOnMaybe f ys = fst <$> go Nothing ys
   where