data-accessor 0.0.1 → 0.1.1

raw patch · 11 files changed

+1203/−163 lines, 11 filesdep −template-haskelldep ~basesetup-changednew-uploaderPVP ok

version bump matches the API change (PVP)

Dependencies removed: template-haskell

Dependency ranges changed: base

API changes (from Hackage documentation)

Files

• Data/Accessor.hs +0/−145
• LICENSE +674/−0
• Setup.lhs +0/−1
• data-accessor.cabal +63/−17
• src/Data/Accessor.hs +93/−0
• src/Data/Accessor/Basic.hs +124/−0
• src/Data/Accessor/BinaryRead.hs +81/−0
• src/Data/Accessor/Example.hs +88/−0
• src/Data/Accessor/MonadState.hs +15/−0
• src/Data/Accessor/Show.hs +39/−0
• src/Data/Accessor/Tuple.hs +26/−0

@@ -1,145 +0,0 @@-{-# LANGUAGE TemplateHaskell, CPP #-}---- |This module provides a simple abstract data type for--- a piece of a data stucture that can be read from and--- written to.  It provides an automatic Template Haskell--- routine to scour data type definitions and generate--- accessor objects for them automatically.--module Data.Accessor-    ( Accessor(..)-    , nameDeriveAccessors, deriveAccessors-    , getA, putA, modA-    , (.>), (<.), (=:)-    )-where--import Language.Haskell.TH-import Language.Haskell.TH.Syntax-import Data.Maybe (catMaybes)-import Control.Monad (guard)-import Control.Monad.State---- |An @Accessor s a@ is an object that encodes how to--- get and put a subject of type @a@ out of/into an object--- of type @s@.--- --- In order for an instance of this data structure @a@ to be--- an "Accessor", it must obey the following laws:--- --- > getVal a (setVal a x s) = x--- > setVal a (getVal a s) s = s-data Accessor s a-    = Accessor { getVal :: s -> a-               , setVal :: a -> s -> s-               }--infixl 9 .> --- |Accessor composition.-(.>) :: Accessor a b -> Accessor b c -> Accessor a c-f .> g = -    Accessor { getVal = getVal g . getVal f-             , setVal = \c a -> setVal f (setVal g c (getVal f a)) a-             }--infixr 9 <.--- |Accessor composition the other direction. --- --- > (<.) = flip (.>)-(<.) :: Accessor b c -> Accessor a b -> Accessor a c-(<.) = flip (.>)--infix 1 =:--- |An "assignment operator" for state monads.  ------ > (=:) = putA-(=:) :: MonadState s m => Accessor s a -> a -> m ()-(=:) = putA---- |A structural dereference function for state monads.-getA :: MonadState s m => Accessor s a -> m a-getA a = liftM (getVal a) get---- |A structural assignment function for state monads.-putA :: MonadState s m => Accessor s a -> a -> m ()-putA a x = get >>= put . setVal a x---- |A structural modification function for state monads.-modA :: MonadState s m => Accessor s a -> (a -> a) -> m ()-modA a f = liftM f (getA a) >>= putA a---- |@deriveAccessors n@ where @n@ is the name of a data type--- declared with @data@ looks through all the declared fields--- of the data type, and for each field ending in an underscore--- generates an accessor of the same name without the underscore.------ It is "nameDeriveAccessors" n f where @f@ satisfies ------ > f (s ++ "_") = Just s--- > f x          = x       -- otherwise------ For example, given the data type:------ > data Score = Score { p1Score_ :: Int--- >                    , p2Score_ :: Int--- >                    , rounds   :: Int--- >                    }------ @deriveAccessors@ will generate the following objects:------ > p1Score :: Accessor Score Int--- > p1Score = Accessor p1Score_ (\x s -> s { p1Score_ = x })--- > p2Score :: Accessor Score Int--- > p2Score = Accessor p2Score_ (\x s -> s { p2Score_ = x })----deriveAccessors :: Name -> Q [Dec]-deriveAccessors n = nameDeriveAccessors n transformName-    where-    transformName s = do-        guard $ not (null s)-        guard $ last s == '_'-        return $ init s---- |@nameDeriveAccessors n f@ where @n@ is the name of a data type--- declared with @data@ and @f@ is a function from names of fields--- in that data type to the name of the corresponding accessor. If--- @f@ returns @Nothing@, then no accessor is generated for that--- field.-nameDeriveAccessors :: Name -> (String -> Maybe String) -> Q [Dec]-nameDeriveAccessors t namer = do-    TyConI (DataD _ name _ cons _) <- reify t-    liftM concat $ mapM makeAccs cons--    where--    makeAccs :: Con -> Q [Dec]-    makeAccs (RecC _ vars) =-        liftM catMaybes $ mapM (\ (name,_,_) -> makeAccFromName name) vars-    makeAccs (ForallC _ _ c) = makeAccs c-    makeAccs _ = return []--    transformName :: Name -> Maybe Name-    transformName (Name occ f) = do-        n <- namer (occString occ)-        return $ Name (mkOccName n) f--    makeAccFromName :: Name -> Q (Maybe Dec)-    makeAccFromName name = do-        case transformName name of-            Nothing -> return Nothing-            Just n -> liftM Just $ makeAcc name n--    -- haddock doesn't grok TH-#ifndef __HADDOCK__--    makeAcc :: Name -> Name -> Q Dec-    makeAcc name accName = do-        body <- [|-            Accessor { getVal = $( return $ VarE name )-                     , setVal = \x s ->-                        $( return $ RecUpdE (VarE 's) [(name, VarE 'x)] )-                     }-                |]-        return $ ValD (VarP accName) (NormalB body) []--#endif

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@@ -1,4 +1,3 @@ #! /usr/bin/env runhaskell- > import Distribution.Simple > main = defaultMain

@@ -1,18 +1,64 @@-Name: data-accessor+Name:             data-accessor+Version:          0.1.1+License:          GPL+License-File:     LICENSE+Author:           Henning Thielemann <haskell@henning-thielemann.de>, Luke Palmer <lrpalmer@gmail.com>+Maintainer:       Henning Thielemann <haskell@henning-thielemann.de>+Homepage:         http://code.haskell.org/data-accessor/+Category:         Data+-- Portability:      Haskell98, not quite because of MTL dependency+Build-Type:       Simple+Build-Depends:    base>=1.0, mtl+Synopsis:         Utilities for accessing and manipulating fields of records Description:-    This module provides a simple abstract data type for-    a piece of a data stucture that can be read from and-    written to.  It provides an automatic Template Haskell-    routine to scour data type definitions and generate-    accessor objects for them automatically.-Version: 0.0.1-Stability: experimental-Synopsis: Automatically generate composable accessors for data types.-License: LGPL-Category: Data-Author: Luke Palmer-Maintainer: lrpalmer@gmail.com-Build-Type: Simple-Build-Depends: base, template-haskell, mtl-Exposed-Modules: Data.Accessor-Extensions: CPP, TemplateHaskell+  In Haskell 98 the name of a record field+  is automatically also the name of a function which gets the value+  of the according field.+  E.g. if we have+  .+    data Pair a b = Pair {first :: a, second :: b}+  .+  then+  .+  > first  :: Pair a b -> a+  > second :: Pair a b -> b+  .+  However for setting or modifying a field value+  we need to use some syntactic sugar, which is often clumsy.+  .+    modifyFirst :: (a -> a) -> (Pair a b -> Pair a b)+    modifyFirst f r\@(Pair {first=a}) = r{first = f a}+  .+  With this package you can define record field accessors+  which allow setting, getting and modifying values easily.+  The package clearly demonstrates the power of the functional approach:+  You can combine accessors of a record and sub-records,+  to make the access look like the fields of the sub-record belong to the main record.+  .+  Example:+  .+  > *Data.Accessor.Example> (first^:second^=10) (('b',7),"hallo")+  > (('b',10),"hallo")+  .+  You can easily manipulate record fields in a 'Control.Monad.State.State' monad,+  you can easily code Show instances that use the Accessor syntax+  and you can parse binary streams into records.+  See @Data.Accessor.Example@ for demonstration of all features.+  .+  It would be great if in revised Haskell versions the names of record fields+  are automatically 'Data.Accessor.Accessor's+  rather than plain @get@ functions.+  The package @data-accessor-template@ provides Template Haskell functions+  for automated generation of 'Data.Acesssor.Accessor's.+GHC-Options:      -Wall+Tested-With:      GHC==6.4.1 && ==6.8.2+Hs-Source-Dirs:   src+Exposed-Modules:+  Data.Accessor+  Data.Accessor.Basic+  Data.Accessor.Show+  Data.Accessor.Tuple+  Data.Accessor.BinaryRead+  Data.Accessor.MonadState+Other-Modules:+  Data.Accessor.Example

@@ -0,0 +1,93 @@+{- |+This module provides a simple abstract data type for+a piece of a data stucture that can be read from and+written to.+In contrast to "Data.Accessor.Basic" it is intended for unqualified import.+-}+module Data.Accessor+    ( Accessor, accessor, setVal, getVal,+      getA, putA, (=:), modA,+      (.>), (<.),+    )+where++import qualified Data.Accessor.Basic as Accessor+import qualified Data.Accessor.MonadState as State+import Control.Monad.State (MonadState, )++-- |An @Accessor s a@ is an object that encodes how to+-- get and put a subject of type @a@ out of/into an object+-- of type @s@.+--+-- In order for an instance of this data structure @a@ to be+-- an 'Accessor', it must obey the following laws:+--+-- > getVal a (setVal a x s) = x+-- > setVal a (getVal a s) s = s+type Accessor s a = Accessor.T s a+++-- |Construct an 'Accessor' from a @get@ and a @set@ method.+--+accessor ::+      (s -> a)       {- ^ get method -}+   -> (a -> s -> s)  {- ^ set method -}+   -> Accessor s a+accessor = flip Accessor.fromSetGet++-- |Get a value from a record field that is specified by an Accessor+getVal ::+      Accessor s a   {- ^ record field -}+   -> s              {- ^ record -}+   -> a              {- ^ value of the field in the record -}+getVal = Accessor.get++-- |Set a value of a record field that is specified by an Accessor+setVal ::+      Accessor s a   {- ^ record field  @f@ -}+   -> a              {- ^ value @x@ to be set -}+   -> s              {- ^ original record -}+   -> s              {- ^ new record with field @f@ changed to @x@ -}+setVal = Accessor.set++++infixl 9 .>++{- |+Accessor composition:+Combine an accessor with an accessor to a sub-field.+Speak \"stack\".+-}+(.>) :: Accessor a b -> Accessor b c -> Accessor a c+(.>) = (Accessor..>)++infixr 9 <.+{- |+Accessor composition the other direction.++> (<.) = flip (.>)+-}+(<.) :: Accessor b c -> Accessor a b -> Accessor a c+(<.) = (Accessor.<.)++++infix 1 =:+-- |An \"assignment operator\" for state monads.+--+-- > (=:) = putA+(=:) :: MonadState s m => Accessor s a -> a -> m ()+(=:) = putA++-- |A structural dereference function for state monads.+getA :: MonadState s m => Accessor s a -> m a+getA = State.get++-- |A structural assignment function for state monads.+putA :: MonadState s m => Accessor s a -> a -> m ()+putA = State.set++-- |A structural modification function for state monads.+modA :: MonadState s m => Accessor s a -> (a -> a) -> m ()+modA = State.modify

@@ -0,0 +1,124 @@+{- |+This module defines the @Accessor@ type.+It should be imported with qualification.+-}+module Data.Accessor.Basic (+   T, fromSetGet, fromLens,+   set, setMany, compose, (^=),+   get, (^.),+   modify, (^:),+   ($%), (<.), (.>),+   ) where++{- |+The access functions we propose, look very similar to those+needed for List.mapAccumL (but parameter order is swapped) and State monad.+They get the new value of the field and the record+and return the old value of the field and the record with the updated field.+-}+newtype T r a  =  Cons {decons :: a -> r -> (a, r)}++fromSetGet :: (a -> r -> r) -> (r -> a) -> T r a+fromSetGet setF getF =+   Cons $ \x r -> (getF r, setF x r)++fromLens :: (r -> (a, a -> r)) -> T r a+fromLens lens =+   Cons $ \ x r -> let (y,f) = lens r in (y, f x)++{- * Access helper functions similar to State methods -}++{- | Set the value of a field. -}+set :: T r a -> a -> r -> r+set f x = snd . decons f x+++infixr 5 ^=, ^:++infixl 0 $%+++{- |+'set' as infix operator.+This lets us write @first ^= 2+3 $ second ^= 5+7 $ record@.+-}+(^=) :: T r a -> a -> (r -> r)+(^=) = set++{- | Set many fields at once.++This function could also be used for initialisation of record,+if record value with undefined fields is provided.++Drawback:+Since all types in a list must have the same type,+you can set only values of the same type.+-}+setMany :: [r -> (a, r)] -> r -> r+setMany = flip (foldl (\x f -> snd (f x)))++{- |+This is a general function,+but it is especially useful for setting many values of different type at once.+-}+compose :: [r -> r] -> r -> r+compose = flip (foldl (flip id))++{- | Get the value of a field. -}+get :: T r a -> r -> a+get f = fst . decons f undefined++infixl 9 ^.++{- |+'get' as infix operator.+This lets us write @record^.field^.subfield@+-}+(^.) :: r -> T r a -> a+(^.) = flip get+++{- | Transform the value of a field by a function. -}+modify :: T r a -> (a -> a) -> (r -> r)+modify f g rOld =+   let (a,rNew) = decons f (g a) rOld+   in  rNew+++{- |+'modify' as infix operator.+This lets us write @record$%field^:subfield^:(1+)@+or @record$%field^:subfield^:(const 1)@.+-}+(^:) :: T r a -> (a -> a) -> (r -> r)+(^:) = modify++{- |+Flipped version of '($)'.+-}+($%) :: a -> (a -> b) -> b+($%) = flip ($)++++infixl 9 .>++{- |+Accessor composition:+Combine an accessor with an accessor to a sub-field.+Speak \"stack\".+-}+(.>) :: T a b -> T b c -> T a c+(.>) f g = Cons $ \ cNew aOld ->+   let (bOld, aNew) = decons f bNew aOld+       (cOld, bNew) = decons g cNew bOld+   in  (cOld, aNew)++infixr 9 <.+{- |+Accessor composition the other direction.++> (<.) = flip (.>)+-}+(<.) :: T b c -> T a b -> T a c+(<.) = flip (.>)

@@ -0,0 +1,81 @@+{- |+Reading records from streams++This is still only for demonstration and might be of not much use+and you should not rely on the interface.+-}+module Data.Accessor.BinaryRead where++import qualified Data.Accessor.Basic as Accessor++import qualified Control.Monad.State as State+import Control.Monad.State (MonadState, StateT, )+import Data.Word (Word8, )+import Data.Char (chr, )++import Prelude hiding (any)+++type Stream = [Word8]++class C a where+   any :: ByteSource source => source a++class Monad source => ByteSource source where+   readWord8 :: source Word8++class ByteStream s where+   getWord8 :: Monad m => s -> m (Word8, s)++instance ByteCompatible byte => ByteStream [byte] where+   getWord8 xs =+      case xs of+         (c:cs) -> return (toByte c, cs)+         _ -> fail "ByteStream: no more byte available"++class ByteCompatible byte where+   toByte :: byte -> Word8++instance ByteCompatible Word8 where+   toByte = id++instance (ByteStream s, Monad m) => ByteSource (StateT s m) where+   readWord8 =+      do xs <- State.get+         (c,cs) <- State.lift (getWord8 xs)+         State.put cs+         return c++instance C Word8 where+   any = readWord8++instance C Char where+   any =+      State.liftM (chr . fromIntegral) readWord8++instance C Int where+   any =+      do c0 <- readWord8+         c1 <- readWord8+         c2 <- readWord8+         c3 <- readWord8+         return+            (foldl1 (\acc d -> acc*256+d)+               (map fromIntegral [c0,c1,c2,c3]))+++newtype Parser s r = Parser {runParser :: (r, s) -> Maybe (r, s)}+++field :: (ByteStream s, C a) =>+   Accessor.T r a -> Parser s r+field f =+   Parser $+      uncurry (\r -> State.runStateT $+         fmap (\x -> Accessor.set f x r) any)++record :: [Parser s r] -> Parser s r+record ps =+   Parser $ flip (foldl (>>=)) (map runParser ps) . Just++-- TOOD: writer

@@ -0,0 +1,88 @@+module Data.Accessor.Example where++import Data.Accessor.Basic ((.>), ($%), (^.), (^:), (^=), )+import Data.Accessor.Tuple (first, second, )++import qualified Data.Accessor.Basic as Accessor+import qualified Data.Accessor.BinaryRead as Read+import qualified Data.Accessor.Show as Show++import qualified Data.Accessor.MonadState as AState+import Control.Monad.State (State)+import Data.Char (ord, )++import Prelude hiding (init)+++{- * Example accesses -}++{- | Example of using 'set', 'get', 'modify'. -}+plain :: Int+plain =+   Accessor.get second $+   Accessor.modify second succ $+   Accessor.set first 'a' $+   ('b',7)++state :: State (Char,Int) Int+state =+   do AState.set first 'a'+      AState.modify second succ+      AState.get second++init :: (Char,Int)+init =+   Accessor.compose+      [Accessor.set first 'b',+       Accessor.modify first succ,+       Accessor.set second 7]+      (undefined,undefined)+--   setMany [first 'b', second 7] (undefined,undefined)++initInfix :: (Char,Int)+initInfix =+   (undefined,undefined)+   $% first ^= 'b'+   $% first ^: succ+   $% second ^= 7++read :: Maybe ((Char,Int), Read.Stream)+read =+   Read.runParser+      (Read.record [Read.field first, Read.field second])+      ((undefined,undefined),+       fromIntegral (ord 'c') : 59 : 154 : 202 : 0 : [])++infix0 :: Int+infix0 =+   (('b',7),"hallo")^.first^.second++infix1 :: ((Char, Int), String)+infix1 =+   (('b',7),"hallo")$%first^:second^:(1+)++infix2 :: ((Char, Int), String)+infix2 =+   (('b',7),"hallo")$%first^:second^=10++infix3 :: Int+infix3 =+   (('b',7),"hallo")^.(first.>second)++infix4 :: ((Char, Int), String)+infix4 =+   (('b',7),"hallo")$%(first.>second)^:(1+)+++showsPair :: Int -> (Char, Int) -> ShowS+showsPair =+   Show.showsPrec+      [Show.field "first"  first,+       Show.field "second" second]+      "init" init++show0 :: String+show0 = showsPair 11 init ""++show1 :: String+show1 = showsPair 5 ('d',8) ""

@@ -0,0 +1,15 @@+{- | Access helper functions in a State monad -}+module Data.Accessor.MonadState where++import qualified Data.Accessor.Basic as Accessor+import qualified Control.Monad.State as State+import Control.Monad.State (MonadState, )++set :: MonadState r m => Accessor.T r a -> a -> m ()+set f x = State.modify (Accessor.set f x)++get :: MonadState r m => Accessor.T r a -> m a+get f = State.gets (Accessor.get f)++modify :: MonadState r m => Accessor.T r a -> (a -> a) -> m ()+modify f g = State.modify (Accessor.modify f g)

@@ -0,0 +1,39 @@+{- |+Support for creating Show instances using the accessors.+-}+module Data.Accessor.Show where++import qualified Data.Accessor.Basic as Accessor++import Data.Maybe (catMaybes)++import qualified Text.Show as Show+import Prelude hiding (showsPrec)+++toMaybe :: Bool -> a -> Maybe a+toMaybe False _ = Nothing+toMaybe True  x = Just x++field :: (Show a, Eq a) =>+   String -> Accessor.T r a -> r -> r -> Maybe ShowS+field name acc deflt record =+   let x = Accessor.get acc record+   in  toMaybe+          (x /= Accessor.get acc deflt)+          (showString name . showString " ^= " . Show.showsPrec 5 x)++showsPrec ::+   [r -> r -> Maybe ShowS] -> String -> r -> Int -> r -> ShowS+showsPrec fields defltName deflt p record =+   let calls =+          catMaybes $+          map (\f -> f deflt record) $+          fields+   in  if null calls+         then showString defltName+         else showParen (p>0)+                 (foldr+                     (\acc s -> acc . showString " $ " . s)+                     (showString defltName)+                     calls)

@@ -0,0 +1,26 @@+module Data.Accessor.Tuple where++import qualified Data.Accessor.Basic as Accessor++{- * Example accessors for the pair type -}++{- | Access to the first value of a pair. -}+first :: Accessor.T (a,b) a+first = Accessor.fromSetGet (\x (_,y) -> (x,y)) fst++{- | Access to the second value of a pair. -}+second :: Accessor.T (a,b) b+second = Accessor.fromSetGet (\y (x,_) -> (x,y)) snd+++{- | Access to the first value of a triple. -}+first3 :: Accessor.T (a,b,c) a+first3 = Accessor.fromLens $ \(xOld,y,z) -> (xOld, \xNew -> (xNew,y,z))++{- | Access to the second value of a triple. -}+second3 :: Accessor.T (a,b,c) b+second3 = Accessor.fromLens $ \(x,yOld,z) -> (yOld, \yNew -> (x,yNew,z))++{- | Access to the third value of a triple. -}+third3 :: Accessor.T (a,b,c) c+third3 = Accessor.fromLens $ \(x,y,zOld) -> (zOld, \zNew -> (x,y,zNew))