Data.Tagged

tagged-0.8.6.1: Haskell 98 phantom types to avoid unsafely passing dummy arguments

Copyright | 2009-2015 Edward Kmett
License | BSD3
Maintainer | Edward Kmett <ekmett@gmail.com>
Stability | experimental
Portability | portable
Safe Haskell | Safe
Language | Haskell98

Data.Tagged

Contents

- Tagged values
- Conversion
- Proxy methods GHC dropped

Description

Synopsis

- newtype Tagged s b = Tagged {
  - unTagged :: b
  }
- retag :: Tagged s b -> Tagged t b
- untag :: Tagged s b -> b
- tagSelf :: a -> Tagged a a
- untagSelf :: Tagged a a -> a
- asTaggedTypeOf :: s -> tagged s b -> s
- witness :: Tagged a b -> a -> b
- proxy :: Tagged s a -> proxy s -> a
- unproxy :: (Proxy s -> a) -> Tagged s a
- tagWith :: proxy s -> a -> Tagged s a
- reproxy :: proxy a -> Proxy b

# Tagged values

newtype Tagged s b #

A ``Tagged` s b` value is a value `b` with an attached phantom type `s`. This can be used in place of the more traditional but less safe idiom of passing in an undefined value with the type, because unlike an `(s -> b)`, a ``Tagged` s b` can't try to use the argument `s` as a real value.

Moreover, you don't have to rely on the compiler to inline away the extra argument, because the newtype is "free"

`Tagged` has kind `k -> * -> *` if the compiler supports `PolyKinds`, therefore there is an extra `k` showing in the instance haddocks that may cause confusion.

Constructors

Tagged |
Fields unTagged :: b

#### Instances

Instances details

Generic1 (Tagged s :: Type -> Type) # |
Instance details Defined in Data.Tagged Associated Types type Rep1 (Tagged s) :: k -> Type Methods from1 :: forall (a :: k). Tagged s a -> Rep1 (Tagged s) a to1 :: forall (a :: k). Rep1 (Tagged s) a -> Tagged s a
Bifoldable (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods bifold :: Monoid m => Tagged m m -> m bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Tagged a b -> m bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Tagged a b -> c bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Tagged a b -> c
Bifunctor (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods bimap :: (a -> b) -> (c -> d) -> Tagged a c -> Tagged b d first :: (a -> b) -> Tagged a c -> Tagged b c second :: (b -> c) -> Tagged a b -> Tagged a c
Bitraversable (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Tagged a b -> f (Tagged c d)
Eq2 (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Tagged a c -> Tagged b d -> Bool
Ord2 (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Tagged a c -> Tagged b d -> Ordering
Read2 (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (Tagged a b) liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [Tagged a b] liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (Tagged a b) liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [Tagged a b]
Show2 (Tagged :: Type -> Type -> Type) # |
Instance details Defined in Data.Tagged Methods liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> Tagged a b -> ShowS liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [Tagged a b] -> ShowS
Foldable (Tagged s) # |
Instance details Defined in Data.Tagged Methods fold :: Monoid m => Tagged s m -> m foldMap :: Monoid m => (a -> m) -> Tagged s a -> m foldMap' :: Monoid m => (a -> m) -> Tagged s a -> m foldr :: (a -> b -> b) -> b -> Tagged s a -> b foldr' :: (a -> b -> b) -> b -> Tagged s a -> b foldl :: (b -> a -> b) -> b -> Tagged s a -> b foldl' :: (b -> a -> b) -> b -> Tagged s a -> b foldr1 :: (a -> a -> a) -> Tagged s a -> a foldl1 :: (a -> a -> a) -> Tagged s a -> a toList :: Tagged s a -> [a] null :: Tagged s a -> Bool length :: Tagged s a -> Int elem :: Eq a => a -> Tagged s a -> Bool maximum :: Ord a => Tagged s a -> a minimum :: Ord a => Tagged s a -> a sum :: Num a => Tagged s a -> a product :: Num a => Tagged s a -> a
Eq1 (Tagged s) # |
Instance details Defined in Data.Tagged Methods liftEq :: (a -> b -> Bool) -> Tagged s a -> Tagged s b -> Bool
Ord1 (Tagged s) # |
Instance details Defined in Data.Tagged Methods liftCompare :: (a -> b -> Ordering) -> Tagged s a -> Tagged s b -> Ordering
Read1 (Tagged s) # |
Instance details Defined in Data.Tagged Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Tagged s a) liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Tagged s a] liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Tagged s a) liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Tagged s a]
Show1 (Tagged s) # |
Instance details Defined in Data.Tagged Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Tagged s a -> ShowS liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Tagged s a] -> ShowS
Traversable (Tagged s) # |
Instance details Defined in Data.Tagged Methods traverse :: Applicative f => (a -> f b) -> Tagged s a -> f (Tagged s b) sequenceA :: Applicative f => Tagged s (f a) -> f (Tagged s a) mapM :: Monad m => (a -> m b) -> Tagged s a -> m (Tagged s b) sequence :: Monad m => Tagged s (m a) -> m (Tagged s a)
Applicative (Tagged s) # |
Instance details Defined in Data.Tagged Methods pure :: a -> Tagged s a (<*>) :: Tagged s (a -> b) -> Tagged s a -> Tagged s b liftA2 :: (a -> b -> c) -> Tagged s a -> Tagged s b -> Tagged s c (*>) :: Tagged s a -> Tagged s b -> Tagged s b (<*) :: Tagged s a -> Tagged s b -> Tagged s a
Functor (Tagged s) # |
Instance details Defined in Data.Tagged Methods fmap :: (a -> b) -> Tagged s a -> Tagged s b (<$) :: a -> Tagged s b -> Tagged s a
Monad (Tagged s) # |
Instance details Defined in Data.Tagged Methods (>>=) :: Tagged s a -> (a -> Tagged s b) -> Tagged s b (>>) :: Tagged s a -> Tagged s b -> Tagged s b return :: a -> Tagged s a
(Data s, Data b) => Data (Tagged s b) # |
Instance details Defined in Data.Tagged Methods gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> Tagged s b -> c (Tagged s b) gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Tagged s b) toConstr :: Tagged s b -> Constr dataTypeOf :: Tagged s b -> DataType dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Tagged s b)) dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Tagged s b)) gmapT :: (forall b0. Data b0 => b0 -> b0) -> Tagged s b -> Tagged s b gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Tagged s b -> r gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Tagged s b -> r gmapQ :: (forall d. Data d => d -> u) -> Tagged s b -> [u] gmapQi :: Int -> (forall d. Data d => d -> u) -> Tagged s b -> u gmapM :: Monad m => (forall d. Data d => d -> m d) -> Tagged s b -> m (Tagged s b) gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Tagged s b -> m (Tagged s b) gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Tagged s b -> m (Tagged s b)
IsString a => IsString (Tagged s a) # |
Instance details Defined in Data.Tagged Methods fromString :: String -> Tagged s a
Storable a => Storable (Tagged s a) # |
Instance details Defined in Data.Tagged Methods sizeOf :: Tagged s a -> Int alignment :: Tagged s a -> Int peekElemOff :: Ptr (Tagged s a) -> Int -> IO (Tagged s a) pokeElemOff :: Ptr (Tagged s a) -> Int -> Tagged s a -> IO () peekByteOff :: Ptr b -> Int -> IO (Tagged s a) pokeByteOff :: Ptr b -> Int -> Tagged s a -> IO () peek :: Ptr (Tagged s a) -> IO (Tagged s a) poke :: Ptr (Tagged s a) -> Tagged s a -> IO ()
(Semigroup a, Monoid a) => Monoid (Tagged s a) # |
Instance details Defined in Data.Tagged Methods mempty :: Tagged s a mappend :: Tagged s a -> Tagged s a -> Tagged s a mconcat :: [Tagged s a] -> Tagged s a
Semigroup a => Semigroup (Tagged s a) # |
Instance details Defined in Data.Tagged Methods (<>) :: Tagged s a -> Tagged s a -> Tagged s a sconcat :: NonEmpty (Tagged s a) -> Tagged s a stimes :: Integral b => b -> Tagged s a -> Tagged s a
Bits a => Bits (Tagged s a) # |
Instance details Defined in Data.Tagged Methods (.&.) :: Tagged s a -> Tagged s a -> Tagged s a (.|.) :: Tagged s a -> Tagged s a -> Tagged s a xor :: Tagged s a -> Tagged s a -> Tagged s a complement :: Tagged s a -> Tagged s a shift :: Tagged s a -> Int -> Tagged s a rotate :: Tagged s a -> Int -> Tagged s a zeroBits :: Tagged s a bit :: Int -> Tagged s a setBit :: Tagged s a -> Int -> Tagged s a clearBit :: Tagged s a -> Int -> Tagged s a complementBit :: Tagged s a -> Int -> Tagged s a testBit :: Tagged s a -> Int -> Bool bitSizeMaybe :: Tagged s a -> Maybe Int bitSize :: Tagged s a -> Int isSigned :: Tagged s a -> Bool shiftL :: Tagged s a -> Int -> Tagged s a unsafeShiftL :: Tagged s a -> Int -> Tagged s a shiftR :: Tagged s a -> Int -> Tagged s a unsafeShiftR :: Tagged s a -> Int -> Tagged s a rotateL :: Tagged s a -> Int -> Tagged s a rotateR :: Tagged s a -> Int -> Tagged s a popCount :: Tagged s a -> Int
FiniteBits a => FiniteBits (Tagged s a) # |
Instance details Defined in Data.Tagged Methods finiteBitSize :: Tagged s a -> Int countLeadingZeros :: Tagged s a -> Int countTrailingZeros :: Tagged s a -> Int
Bounded b => Bounded (Tagged s b) # |
Instance details Defined in Data.Tagged Methods minBound :: Tagged s b maxBound :: Tagged s b
Enum a => Enum (Tagged s a) # |
Instance details Defined in Data.Tagged Methods succ :: Tagged s a -> Tagged s a pred :: Tagged s a -> Tagged s a toEnum :: Int -> Tagged s a fromEnum :: Tagged s a -> Int enumFrom :: Tagged s a -> [Tagged s a] enumFromThen :: Tagged s a -> Tagged s a -> [Tagged s a] enumFromTo :: Tagged s a -> Tagged s a -> [Tagged s a] enumFromThenTo :: Tagged s a -> Tagged s a -> Tagged s a -> [Tagged s a]
Floating a => Floating (Tagged s a) # |
Instance details Defined in Data.Tagged Methods pi :: Tagged s a exp :: Tagged s a -> Tagged s a log :: Tagged s a -> Tagged s a sqrt :: Tagged s a -> Tagged s a (**) :: Tagged s a -> Tagged s a -> Tagged s a logBase :: Tagged s a -> Tagged s a -> Tagged s a sin :: Tagged s a -> Tagged s a cos :: Tagged s a -> Tagged s a tan :: Tagged s a -> Tagged s a asin :: Tagged s a -> Tagged s a acos :: Tagged s a -> Tagged s a atan :: Tagged s a -> Tagged s a sinh :: Tagged s a -> Tagged s a cosh :: Tagged s a -> Tagged s a tanh :: Tagged s a -> Tagged s a asinh :: Tagged s a -> Tagged s a acosh :: Tagged s a -> Tagged s a atanh :: Tagged s a -> Tagged s a log1p :: Tagged s a -> Tagged s a expm1 :: Tagged s a -> Tagged s a log1pexp :: Tagged s a -> Tagged s a log1mexp :: Tagged s a -> Tagged s a
RealFloat a => RealFloat (Tagged s a) # |
Instance details Defined in Data.Tagged Methods floatRadix :: Tagged s a -> Integer floatDigits :: Tagged s a -> Int floatRange :: Tagged s a -> (Int, Int) decodeFloat :: Tagged s a -> (Integer, Int) encodeFloat :: Integer -> Int -> Tagged s a exponent :: Tagged s a -> Int significand :: Tagged s a -> Tagged s a scaleFloat :: Int -> Tagged s a -> Tagged s a isNaN :: Tagged s a -> Bool isInfinite :: Tagged s a -> Bool isDenormalized :: Tagged s a -> Bool isNegativeZero :: Tagged s a -> Bool isIEEE :: Tagged s a -> Bool atan2 :: Tagged s a -> Tagged s a -> Tagged s a
Generic (Tagged s b) # |
Instance details Defined in Data.Tagged Associated Types type Rep (Tagged s b) :: Type -> Type Methods from :: Tagged s b -> Rep (Tagged s b) x to :: Rep (Tagged s b) x -> Tagged s b
Ix b => Ix (Tagged s b) # |
Instance details Defined in Data.Tagged Methods range :: (Tagged s b, Tagged s b) -> [Tagged s b] index :: (Tagged s b, Tagged s b) -> Tagged s b -> Int unsafeIndex :: (Tagged s b, Tagged s b) -> Tagged s b -> Int inRange :: (Tagged s b, Tagged s b) -> Tagged s b -> Bool rangeSize :: (Tagged s b, Tagged s b) -> Int unsafeRangeSize :: (Tagged s b, Tagged s b) -> Int
Num a => Num (Tagged s a) # |
Instance details Defined in Data.Tagged Methods (+) :: Tagged s a -> Tagged s a -> Tagged s a (-) :: Tagged s a -> Tagged s a -> Tagged s a (*) :: Tagged s a -> Tagged s a -> Tagged s a negate :: Tagged s a -> Tagged s a abs :: Tagged s a -> Tagged s a signum :: Tagged s a -> Tagged s a fromInteger :: Integer -> Tagged s a
Read b => Read (Tagged s b) # |
Instance details Defined in Data.Tagged Methods readsPrec :: Int -> ReadS (Tagged s b) readList :: ReadS [Tagged s b] readPrec :: ReadPrec (Tagged s b) readListPrec :: ReadPrec [Tagged s b]
Fractional a => Fractional (Tagged s a) # |
Instance details Defined in Data.Tagged Methods (/) :: Tagged s a -> Tagged s a -> Tagged s a recip :: Tagged s a -> Tagged s a fromRational :: Rational -> Tagged s a
Integral a => Integral (Tagged s a) # |
Instance details Defined in Data.Tagged Methods quot :: Tagged s a -> Tagged s a -> Tagged s a rem :: Tagged s a -> Tagged s a -> Tagged s a div :: Tagged s a -> Tagged s a -> Tagged s a mod :: Tagged s a -> Tagged s a -> Tagged s a quotRem :: Tagged s a -> Tagged s a -> (Tagged s a, Tagged s a) divMod :: Tagged s a -> Tagged s a -> (Tagged s a, Tagged s a) toInteger :: Tagged s a -> Integer
Real a => Real (Tagged s a) # |
Instance details Defined in Data.Tagged Methods toRational :: Tagged s a -> Rational
RealFrac a => RealFrac (Tagged s a) # |
Instance details Defined in Data.Tagged Methods properFraction :: Integral b => Tagged s a -> (b, Tagged s a) truncate :: Integral b => Tagged s a -> b round :: Integral b => Tagged s a -> b ceiling :: Integral b => Tagged s a -> b floor :: Integral b => Tagged s a -> b
Show b => Show (Tagged s b) # |
Instance details Defined in Data.Tagged Methods showsPrec :: Int -> Tagged s b -> ShowS show :: Tagged s b -> String showList :: [Tagged s b] -> ShowS
NFData b => NFData (Tagged s b) # |
Instance details Defined in Data.Tagged Methods rnf :: Tagged s b -> ()
Eq b => Eq (Tagged s b) # |
Instance details Defined in Data.Tagged Methods (==) :: Tagged s b -> Tagged s b -> Bool (/=) :: Tagged s b -> Tagged s b -> Bool
Ord b => Ord (Tagged s b) # |
Instance details Defined in Data.Tagged Methods compare :: Tagged s b -> Tagged s b -> Ordering (<) :: Tagged s b -> Tagged s b -> Bool (<=) :: Tagged s b -> Tagged s b -> Bool (>) :: Tagged s b -> Tagged s b -> Bool (>=) :: Tagged s b -> Tagged s b -> Bool max :: Tagged s b -> Tagged s b -> Tagged s b min :: Tagged s b -> Tagged s b -> Tagged s b
type Rep1 (Tagged s :: Type -> Type) # |
Instance details Defined in Data.Tagged type Rep1 (Tagged s :: Type -> Type) = D1 ('MetaData "Tagged" "Data.Tagged" "tagged-0.8.6.1-AnEXtcauaoFD9GeS6yspTu" 'True) (C1 ('MetaCons "Tagged" 'PrefixI 'True) (S1 ('MetaSel ('Just "unTagged") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))
type Rep (Tagged s b) # |
Instance details Defined in Data.Tagged type Rep (Tagged s b) = D1 ('MetaData "Tagged" "Data.Tagged" "tagged-0.8.6.1-AnEXtcauaoFD9GeS6yspTu" 'True) (C1 ('MetaCons "Tagged" 'PrefixI 'True) (S1 ('MetaSel ('Just "unTagged") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 b)))

retag :: Tagged s b -> Tagged t b #

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
    retagSucc :: Tagged n a -> Tagged (Succ n) a
    retagSucc = retag

untag :: Tagged s b -> b #

Alias for `unTagged`

tagSelf :: a -> Tagged a a #

Tag a value with its own type.

untagSelf :: Tagged a a -> a #

`untagSelf` is a type-restricted version of `untag`.

asTaggedTypeOf :: s -> tagged s b -> s #

`asTaggedTypeOf` 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.

witness :: Tagged a b -> a -> b #

# Conversion

proxy :: Tagged s a -> proxy s -> a #

Convert from a `Tagged` representation to a representation based on a `Proxy`.

unproxy :: (Proxy s -> a) -> Tagged s a #

Convert from a representation based on a `Proxy` to a `Tagged` representation.

tagWith :: proxy s -> a -> Tagged s a #

Another way to convert a proxy to a tag.

# Proxy methods GHC dropped

reproxy :: proxy a -> Proxy b #

Some times you need to change the proxy you have lying around. Idiomatic usage is to make a new combinator for the relationship between the proxies that you want to enforce, and define that combinator using `reproxy`.

    data Succ n
    reproxySucc :: proxy n -> Proxy (Succ n)
    reproxySucc = reproxy