phantom-state (empty) → 0.1.0.0

raw patch · 4 files changed

+131/−0 lines, 4 filesdep +basedep +transformerssetup-changed

Dependencies added: base, transformers

Files

• Control/Monad/PhantomState.hs +77/−0
• LICENSE +30/−0
• Setup.hs +2/−0
• phantom-state.cabal +22/−0

@@ -0,0 +1,77 @@++-- | Phantom Monad State Transformer constructor and functions.+module Control.Monad.PhantomState (+    PhantomStateT (..)+  , PhantomState+  , useState+  , changeState+  , runPhantomStateT+  , runPhantomState+  ) where++import Control.Applicative+import Control.Monad.Trans.Class+import Data.Functor.Identity++-- | The Phantom State Monad Transformer is like the+--   State Monad Transformer, but it does not hold+--   any value.+newtype PhantomStateT s m a = PhantomStateT (s -> m s)++-- | Type synonym of 'PhantomStateT' where the underlying 'Monad' is the 'Identity' monad.+type PhantomState s a = PhantomStateT s Identity a++-- | Perform an applicative action using the current state, leaving+--   the state unchanged.+useState :: Applicative m => (s -> m a) -> PhantomStateT s m ()+{-# INLINE useState #-}+useState f = PhantomStateT $ \x -> f x *> pure x++-- | Modify the state using a pure function.+changeState :: Applicative m => (s -> s) -> PhantomStateT s m ()+{-# INLINE changeState #-}+changeState f = PhantomStateT $ pure . f++-- | Perform a phantom state computation by setting an initial state+--   and running all the actions from there.+runPhantomStateT :: PhantomStateT s m a -- ^ Phantom state computation+                 -> s -- ^ Initial state+                 -> m s -- ^ Final result+{-# INLINE runPhantomStateT #-}+runPhantomStateT (PhantomStateT f) x = f x++-- | Specialized version of 'runPhantomStateT' where the underlying+--   'Monad' is the 'Identity' monad.+runPhantomState :: PhantomState s a -- ^ Phantom state computation+                -> s -- ^ Initial state+                -> s -- ^ Final result+{-# INLINE runPhantomState #-}+runPhantomState f = runIdentity . runPhantomStateT f++-- Instances++instance Functor (PhantomStateT s m) where+  {-# INLINE fmap #-}+  fmap _ (PhantomStateT f) = PhantomStateT f++instance Monad m => Applicative (PhantomStateT s m) where+  {-# INLINE pure #-}+  pure _ = PhantomStateT return+  {-# INLINE (<*>) #-}+  PhantomStateT f <*> PhantomStateT g = PhantomStateT (\x -> f x >>= g)+  {-# INLINE  (*>) #-}+  PhantomStateT f  *> PhantomStateT g = PhantomStateT (\x -> f x >>= g)+  {-# INLINE (<*) #-}+  PhantomStateT f <*  PhantomStateT g = PhantomStateT (\x -> f x >>= g)++instance Monad m => Monad (PhantomStateT s m) where+  {-# INLINE return #-}+  return = pure+  {-# INLINE (>>=) #-}+  x >>= f = x *> f undefined+  {-# INLINE (>>) #-}+  (>>) = (*>)++instance MonadTrans (PhantomStateT s) where+  {-# INLINE lift #-}+  lift m = PhantomStateT (\x -> m >> return x)

@@ -0,0 +1,30 @@+Copyright (c) 2014, Daniel Díaz++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 Daniel Díaz 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.

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

@@ -0,0 +1,22 @@+name:                phantom-state+version:             0.1.0.0+synopsis:            Phantom State Monad Transformer. Like State Monad, but without values.+description:         A monad transformer that mimics the State Monad Transformer from the+                     <http://hackage.haskell.org/package/transformers transformers> package,+                     but dropping the values. In those cases that you want to use the State+                     Monad but you only care about how the state changes, use this library+                     to earn a plus of efficiency.+license:             BSD3+license-file:        LICENSE+author:              Daniel Díaz+maintainer:          dhelta.diaz@gmail.com+category:            Control+build-type:          Simple+cabal-version:       >=1.10++library+  exposed-modules:     Control.Monad.PhantomState+  build-depends:       base == 4.*+                     , transformers >= 0.3 && < 0.5+  default-language:    Haskell2010+  ghc-options: -O2 -Wall