witherable (empty) → 0.0

raw patch · 4 files changed

+113/−0 lines, 4 filesdep +basedep +containersdep +hashablesetup-changed

Dependencies added: base, containers, hashable, transformers, unordered-containers, vector

Files

LICENSE +30/−0
Setup.hs +2/−0
src/Data/Witherable.hs +56/−0
witherable.cabal +25/−0

+ LICENSE view

@@ -0,0 +1,30 @@+Copyright (c) 2014, Fumiaki Kinoshita
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Fumiaki Kinoshita nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

+ Setup.hs view

@@ -0,0 +1,2 @@+import Distribution.Simple
+main = defaultMain

+ src/Data/Witherable.hs view

@@ -0,0 +1,56 @@+module Data.Witherable where
+import qualified Data.Maybe as Maybe
+import qualified Data.IntMap.Lazy as IM
+import qualified Data.Map.Lazy as M
+import qualified Data.Sequence as S
+import qualified Data.Vector as V
+import qualified Data.HashMap.Strict as HM
+import Control.Applicative
+import qualified Data.Traversable as T
+import qualified Data.Foldable as F
+import Data.Hashable
+import Data.Functor.Identity
+
+-- | Like `traverse`, but you can remove elements instead of updating them.
+-- @traverse f = wither (fmap Just . f)@
+-- Minimal complete definition: `wither` or `catMaybes`.
+class T.Traversable t => Witherable t where
+
+  wither :: Applicative f => (a -> f (Maybe b)) -> t a -> f (t b)
+  wither f = fmap catMaybes . T.traverse f
+
+  catMaybes :: Witherable t => t (Maybe a) -> t a
+  catMaybes = runIdentity . wither pure
+
+  witherM :: Monad m => (a -> m (Maybe b)) -> t a -> m (t b)
+  witherM f = unwrapMonad . wither (WrapMonad . f)
+
+-- | 'blightM' is 'witherM' with its arguments flipped.
+blightM :: (Monad m, Witherable t) => t a -> (a -> m (Maybe b)) -> m (t b)
+blightM = flip witherM
+{-# INLINE blightM #-}
+
+instance Witherable Maybe where
+  wither _ Nothing = pure Nothing
+  wither f (Just a) = f a
+
+instance Witherable [] where
+  wither f = fmap Maybe.catMaybes . T.traverse f
+
+instance Witherable IM.IntMap where
+  wither f = fmap IM.fromList . wither (\(i, a) -> fmap ((,) i) <$> f a) . IM.toList
+
+instance Ord k => Witherable (M.Map k) where
+  wither f = fmap M.fromList . wither (\(i, a) -> fmap ((,) i) <$> f a) . M.toList
+
+instance (Eq k, Hashable k) => Witherable (HM.HashMap k) where
+  wither f = fmap HM.fromList . wither (\(i, a) -> fmap ((,) i) <$> f a) . HM.toList
+
+instance Witherable (Const r) where
+  wither _ (Const r) = pure (Const r)
+
+instance Witherable V.Vector where
+  wither f = fmap V.fromList . wither f . V.toList
+
+instance Witherable S.Seq where
+  wither f = fmap S.fromList . wither f . F.toList

+ witherable.cabal view

@@ -0,0 +1,25 @@+-- Initial witherable.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                witherable
+version:             0.0
+synopsis:            Generalization of catMaybes
+-- description:         
+homepage:            https://github.com/fumieval/witherable
+license:             BSD3
+license-file:        LICENSE
+author:              Fumiaki Kinoshita
+maintainer:          Fumiaki Kinoshita <fumiexcel@gmail.com>
+copyright:           Copyright (c) 2014 Fumiaki Kinoshita
+category:            Data
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+library
+  exposed-modules:     Data.Witherable
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base == 4.*, containers, vector, unordered-containers, hashable, transformers
+  hs-source-dirs:      src
+  default-language:    Haskell2010