monad-extras 0.5.7 → 0.5.8

raw patch · 2 files changed

+26/−2 lines, 2 files

Files

• Control/Monad/Extra.hs +25/−1
• monad-extras.cabal +1/−1

@@ -5,13 +5,16 @@ module Control.Monad.Extra where  import Control.Applicative-import Control.Monad+import Control.Monad hiding (mapM_) import Control.Monad.IO.Class import Control.Monad.STM import Control.Monad.Trans.Cont import Control.Monad.Trans.Control import Data.IORef+import Data.Foldable import Data.Maybe (catMaybes)+import Data.Monoid+import Prelude hiding (mapM_) import System.IO.Unsafe  -- | Synonym for @return ()@.@@ -235,3 +238,24 @@         Nothing -> return []         Just x' -> (x':) `liftM` iterateMaybeM f x' +-- | A monadic unfold.+unfoldM :: Monad m => (s -> m (Maybe (a, s))) -> s -> m [a]+unfoldM f s = do+    mres <- f s+    case mres of+        Nothing      -> return []+        Just (a, s') -> liftM2 (:) (return a) (unfoldM f s')++-- | A monadic unfold which does not interact with the result.  The only action+--   this function provides therefore is to iterate through the values in 's'+--   and produce side-effects in IO.+unfoldM_ :: Monad m => (s -> m (Maybe s)) -> s -> m ()+unfoldM_ f s = f s >>= mapM_ (unfoldM_ f)++-- | A monadic unfold.+unfoldMapM :: (Monad m, Monoid a) => (s -> m (Maybe (a, s))) -> s -> m a+unfoldMapM f s = do+    mres <- f s+    case mres of+        Nothing      -> return mempty+        Just (a, s') -> liftM2 mappend (return a) (unfoldMapM f s')

@@ -1,5 +1,5 @@ name:           monad-extras-version:        0.5.7+version:        0.5.8 synopsis:       Extra utility functions for working with monads -- description: homepage:       http://github.com/jwiegley/monad-extras