Fix Haddock markup.

[comptalang.git] / lib / Hcompta / Lib / Foldable.hs

diff --git a/lib/Hcompta/Lib/Foldable.hs b/lib/Hcompta/Lib/Foldable.hs
index ee0ef96bf9e2c734e078e1ab79b705cf5b94ab56..cfb60a45221a5b5f331f992ea3563e892c6f772d 100644 (file)
--- a/lib/Hcompta/Lib/Foldable.hs
+++ b/lib/Hcompta/Lib/Foldable.hs
@@ -1,13 +1,15 @@
 module Hcompta.Lib.Foldable where
 
-import Data.Monoid
-import Data.Maybe (listToMaybe, maybeToList)
-import Data.Foldable (Foldable, foldMap, foldr)
+import Data.Either (Either(..), either)
+import Data.Foldable (Foldable(..))
+import Data.Function ((.))
+import Data.Maybe (Maybe(..), listToMaybe, maybeToList)
+import Data.Monoid (Monoid(..))
 
 -- | Return the first non-'Nothing' returned by the given function
 --   applied on the elements of a 'Foldable'.
 find :: Foldable t => (a -> Maybe b) -> t a -> Maybe b
-find f = listToMaybe . Data.Foldable.foldMap (maybeToList . f)
+find f = listToMaybe . foldMap (maybeToList . f)
 
 -- | Like 'Data.Either.partitionEithers' but generalized
 --   to work on a 'Foldable' containing 'Monoid's.
@@ -16,8 +18,8 @@ find f = listToMaybe . Data.Foldable.foldMap (maybeToList . f)
 partitionEithers
  :: (Foldable t, Monoid r, Monoid l)
  => t (Either l r) -> (l, r)
-partitionEithers m =
-       Data.Foldable.foldr (either left right) (mempty, mempty) m
+partitionEithers =
+       foldr (either left right) (mempty, mempty)
        where
                left  a ~(l, r) = (a`mappend`l, r)
                right a ~(l, r) = (l, a`mappend`r)
@@ -25,12 +27,15 @@ partitionEithers m =
 -- | Return a tuple of accumulated 'Left's and folded 'Right's
 --   in the given 'Foldable'.
 --
--- NOTE: any lazyness on resulting 'Left's’ 'Monoid' is preserved.
+--   * NOTE: any lazyness on resulting 'Monoid's is preserved.
+--   * WARNING: beware that given an infinite 'Foldable',
+--              the initial 'Right' accumulator will never be appended
+--              to the final 'Right' accumulator.
 accumLeftsAndFoldrRights
  :: (Foldable t, Monoid l)
  => (r -> ra -> ra) -> ra -> t (Either l r) -> (l, ra)
-accumLeftsAndFoldrRights f rempty m =
-       Data.Foldable.foldr (either left right) (mempty, rempty) m
+accumLeftsAndFoldrRights f rempty =
+       foldr (either left right) (mempty, rempty)
        where
                left  a ~(l, r) = (a`mappend`l, r)
                right a ~(l, r) = (l, f a r)