Split off StreamingHelp module

src/StreamingHelp.hs

@@ -0,0 +1,25 @@
+module StreamingHelp 
+    ( minStreamOn
+    , sortStreamOn
+    , StreamOf
+    , module Streaming
+    ) where
+import Streaming
+import qualified Streaming.Prelude as S
+import qualified Control.Foldl as L
+import Data.Function (on)
+
+type StreamOf a = Stream (Of a) Identity ()
+
+minStreamOn :: Ord a => (b -> a) -> StreamOf b -> Maybe b
+{-# INLINE minStreamOn #-}
+minStreamOn f = runIdentity
+    . L.purely S.fold_ (L.minimumBy (compare `on` f))
+
+-- this hopefully also nub the stream in most cases
+--orderStreamOn :: Ord b => (a -> b) -> Stream (Of a) Identity () -> Identity (Of (M.Map b a) ())
+sortStreamOn :: Ord a => (b -> a) -> StreamOf b -> Stream (Of b) Identity ()
+{-# INLINE sortStreamOn #-}
+sortStreamOn f = S.each . runIdentity . L.purely S.fold_ L.map . S.map g
+  where
+    g x = (f x,x)