Use external strict pair package (use strict-tuple-lens also?)

src/FoldlHelp.hs

@@ -1,13 +1,15 @@
-module FoldlHelp
-    ( minimumOn
-    , premapMaybe
-    , module Control.Foldl
-    ) where
+module FoldlHelp (
+    minimumOn,
+    premapMaybe,
+    module Control.Foldl,
+) where
+
 import Control.Foldl
 import MaybeHelp
+import Data.Strict.Tuple
 
 --data Maybe' a = Just' !a | Nothing'
-data Pair a b = !a :!: !b
+--data Pair a b = !a :!: !b
 
 minimumOn :: Ord b => (a -> b) -> Fold a (Maybe a)
 minimumOn f = Fold step Nothing' extract
@@ -22,7 +24,7 @@ minimumOn f = Fold step Nothing' extract
         y = f b
 
 premapMaybe :: (a -> Maybe b) -> Fold b r -> Fold a r
-{-# INLINABLE premapMaybe #-}
+{-# INLINEABLE premapMaybe #-}
 premapMaybe f (Fold step initial extract) = Fold step' initial extract
   where
     step' x a = case f a of