tagged 0.1.0 → 0.1.1

raw patch · 2 files changed

+41/−15 lines, 2 files

Files

• Data/Tagged.hs +39/−14
• tagged.cabal +2/−1

@@ -36,7 +36,8 @@ import Data.Monoid (Monoid(..)) import Data.Default (Default(..)) import Data.Data (Data,Typeable)-import Data.Ix (Ix)+import Data.Ix (Ix(..))+import GHC.Arr (unsafeIndex, unsafeRangeSize) import Text.Read  -- | A @'Tagged' s b@ value is a value @b@ with an attached phantom type @s@.@@ -127,16 +128,27 @@ asTaggedTypeOf = const {-# INLINE asTaggedTypeOf #-} --- | 'selfUntag' +-- | 'untagSelf' is a type-restricted version of 'untag'. untagSelf :: Tagged a a -> a untagSelf (Tagged x) = x {-# INLINE untagSelf #-}  data Proxy p = Proxy-    -- deriving (Eq,Ord,Ix,Show,Read)+    deriving (Eq,Ord,Show,Read,Data,Typeable) +instance Enum (Proxy s) where+    succ _ = error "Proxy.succ"+    pred _ = error "Proxy.pred"+    fromEnum _ = 0+    toEnum 0 = Proxy+    toEnum _ = error "Proxy.toEnum: 0 expected"+    enumFrom _ = [Proxy]+    enumFromThen _ _ = [Proxy]+    enumFromThenTo _ _ _ = [Proxy]+    enumFromTo _ _ = [Proxy]+ {- -Work around for the following GHC bug with deriving:+Work around for the following GHC bug with deriving Ix instances with a phantom type:  Data/Tagged.hs:1:0:     Expecting an ordinary type, but found a type of kind * -> *@@ -148,16 +160,13 @@  -} -instance Enum (Proxy s) where-    succ _ = error "Proxy.succ"-    pred _ = error "Proxy.pred"-    fromEnum _ = 0-    toEnum 0 = Proxy-    toEnum _ = error "Proxy.toEnum: 0 expected"-    enumFrom _ = [Proxy]-    enumFromThen _ _ = [Proxy]-    enumFromThenTo _ _ _ = [Proxy]-    enumFromTo _ _ = [Proxy]+instance Ix (Proxy s) where+    range _ = [Proxy]+    index _ _ = 0+    unsafeIndex _ _ = 0+    inRange _ _ = True+    rangeSize _ = 1+    unsafeRangeSize _ = 1      instance Bounded (Proxy s) where     minBound = Proxy@@ -215,18 +224,34 @@     def = Proxy     {-# INLINE def #-} +-- | Some times you need to change the tag you have lying around.+-- Idiomatic usage is to make a new combinator for the relationship +-- between the tags that you want to enforce, and define that +-- combinator using 'retag'.+--+-- > data Succ n+-- > reproxySucc :: Proxy n -> Proxy (Succ n)+-- > reproxySucc = reproxy reproxy :: Proxy s -> Proxy t reproxy _ = Proxy {-# INLINE reproxy #-} +-- | Convert from a 'Tagged' representation to a representation +-- based on a 'Proxy'. proxy :: Tagged s a -> Proxy s -> a proxy (Tagged x) _ = x {-# INLINE proxy #-} +-- | Convert from a representation based on a 'Proxy' to a 'Tagged' +-- representation. unproxy :: (Proxy s -> a) -> Tagged s a unproxy f = Tagged (f Proxy) {-# INLINE unproxy #-} +-- | 'asProxyTypeOf' is a type-restricted version of 'const'. +-- It is usually used as an infix operator, and its typing forces its first +-- argument (which is usually overloaded) to have the same type as the tag +-- of the second. asProxyTypeOf :: a -> Proxy a -> a asProxyTypeOf = const {-# INLINE asProxyTypeOf #-}

@@ -1,5 +1,5 @@ name:		    tagged-version:	    0.1.0+version:	    0.1.1 license:	    BSD3 license-file:   LICENSE author:		    Edward A. Kmett@@ -7,6 +7,7 @@ stability:	    experimental category:	    Data, Phantom Types synopsis:	    Provides newtype wrappers for phantom types to avoid unsafely passing dummy arguments+homepage:       http://github.com/ekmett/tagged copyright:      2009 Edward A. Kmett description:    Provides newtype wrappers for phantom types to avoid unsafely passing dummy arguments build-type:     Simple