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

Tagged values

newtype Tagged s b Source

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

Bifunctor (Tagged *) Source
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
Monad (Tagged k s) Source
Methods (>>=) :: Tagged k s a -> (a -> Tagged k s b) -> Tagged k s b (>>) :: Tagged k s a -> Tagged k s b -> Tagged k s b return :: a -> Tagged k s a fail :: String -> Tagged k s a
Functor (Tagged k s) Source
Methods fmap :: (a -> b) -> Tagged k s a -> Tagged k s b (<$) :: a -> Tagged k s b -> Tagged k s a
Applicative (Tagged k s) Source
Methods pure :: a -> Tagged k s a (<>) :: Tagged k s (a -> b) -> Tagged k s a -> Tagged k s b (>) :: Tagged k s a -> Tagged k s b -> Tagged k s b (<*) :: Tagged k s a -> Tagged k s b -> Tagged k s a
Foldable (Tagged k s) Source
Methods fold :: Monoid m => Tagged k s m -> m foldMap :: Monoid m => (a -> m) -> Tagged k s a -> m foldr :: (a -> b -> b) -> b -> Tagged k s a -> b foldr' :: (a -> b -> b) -> b -> Tagged k s a -> b foldl :: (b -> a -> b) -> b -> Tagged k s a -> b foldl' :: (b -> a -> b) -> b -> Tagged k s a -> b foldr1 :: (a -> a -> a) -> Tagged k s a -> a foldl1 :: (a -> a -> a) -> Tagged k s a -> a toList :: Tagged k s a -> [a] null :: Tagged k s a -> Bool length :: Tagged k s a -> Int elem :: Eq a => a -> Tagged k s a -> Bool maximum :: Ord a => Tagged k s a -> a minimum :: Ord a => Tagged k s a -> a sum :: Num a => Tagged k s a -> a product :: Num a => Tagged k s a -> a
Traversable (Tagged k s) Source
Methods traverse :: Applicative f => (a -> f b) -> Tagged k s a -> f (Tagged k s b) sequenceA :: Applicative f => Tagged k s (f a) -> f (Tagged k s a) mapM :: Monad m => (a -> m b) -> Tagged k s a -> m (Tagged k s b) sequence :: Monad m => Tagged k s (m a) -> m (Tagged k s a)
Generic1 (Tagged k s) Source
Associated Types type Rep1 (Tagged k s :: * -> ) :: -> * Methods from1 :: Tagged k s a -> Rep1 (Tagged k s) a to1 :: Rep1 (Tagged k s) a -> Tagged k s a
Bounded b => Bounded (Tagged k s b) Source
Methods minBound :: Tagged k s b maxBound :: Tagged k s b
Enum a => Enum (Tagged k s a) Source
Methods succ :: Tagged k s a -> Tagged k s a pred :: Tagged k s a -> Tagged k s a toEnum :: Int -> Tagged k s a fromEnum :: Tagged k s a -> Int enumFrom :: Tagged k s a -> [Tagged k s a] enumFromThen :: Tagged k s a -> Tagged k s a -> [Tagged k s a] enumFromTo :: Tagged k s a -> Tagged k s a -> [Tagged k s a] enumFromThenTo :: Tagged k s a -> Tagged k s a -> Tagged k s a -> [Tagged k s a]
Eq b => Eq (Tagged k s b) Source
Methods (==) :: Tagged k s b -> Tagged k s b -> Bool (/=) :: Tagged k s b -> Tagged k s b -> Bool
Floating a => Floating (Tagged k s a) Source
Methods pi :: Tagged k s a exp :: Tagged k s a -> Tagged k s a log :: Tagged k s a -> Tagged k s a sqrt :: Tagged k s a -> Tagged k s a (**) :: Tagged k s a -> Tagged k s a -> Tagged k s a logBase :: Tagged k s a -> Tagged k s a -> Tagged k s a sin :: Tagged k s a -> Tagged k s a cos :: Tagged k s a -> Tagged k s a tan :: Tagged k s a -> Tagged k s a asin :: Tagged k s a -> Tagged k s a acos :: Tagged k s a -> Tagged k s a atan :: Tagged k s a -> Tagged k s a sinh :: Tagged k s a -> Tagged k s a cosh :: Tagged k s a -> Tagged k s a tanh :: Tagged k s a -> Tagged k s a asinh :: Tagged k s a -> Tagged k s a acosh :: Tagged k s a -> Tagged k s a atanh :: Tagged k s a -> Tagged k s a
Fractional a => Fractional (Tagged k s a) Source
Methods (/) :: Tagged k s a -> Tagged k s a -> Tagged k s a recip :: Tagged k s a -> Tagged k s a fromRational :: Rational -> Tagged k s a
Integral a => Integral (Tagged k s a) Source
Methods quot :: Tagged k s a -> Tagged k s a -> Tagged k s a rem :: Tagged k s a -> Tagged k s a -> Tagged k s a div :: Tagged k s a -> Tagged k s a -> Tagged k s a mod :: Tagged k s a -> Tagged k s a -> Tagged k s a quotRem :: Tagged k s a -> Tagged k s a -> (Tagged k s a, Tagged k s a) divMod :: Tagged k s a -> Tagged k s a -> (Tagged k s a, Tagged k s a) toInteger :: Tagged k s a -> Integer
(Data s, Data b) => Data (Tagged * s b) Source
Methods gfoldl :: (forall d a. Data d => c (d -> a) -> d -> c a) -> (forall g. g -> c g) -> Tagged * s b -> c (Tagged * s b) gunfold :: (forall a r. Data a => c (a -> 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 a. Data a => a -> a) -> Tagged * s b -> Tagged * s b gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Tagged * s b -> r gmapQr :: (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)
Num a => Num (Tagged k s a) Source
Methods (+) :: Tagged k s a -> Tagged k s a -> Tagged k s a (-) :: Tagged k s a -> Tagged k s a -> Tagged k s a (*) :: Tagged k s a -> Tagged k s a -> Tagged k s a negate :: Tagged k s a -> Tagged k s a abs :: Tagged k s a -> Tagged k s a signum :: Tagged k s a -> Tagged k s a fromInteger :: Integer -> Tagged k s a
Ord b => Ord (Tagged k s b) Source
Methods compare :: Tagged k s b -> Tagged k s b -> Ordering (<) :: Tagged k s b -> Tagged k s b -> Bool (<=) :: Tagged k s b -> Tagged k s b -> Bool (>) :: Tagged k s b -> Tagged k s b -> Bool (>=) :: Tagged k s b -> Tagged k s b -> Bool max :: Tagged k s b -> Tagged k s b -> Tagged k s b min :: Tagged k s b -> Tagged k s b -> Tagged k s b
Read b => Read (Tagged k s b) Source
Methods readsPrec :: Int -> ReadS (Tagged k s b) readList :: ReadS [Tagged k s b] readPrec :: ReadPrec (Tagged k s b) readListPrec :: ReadPrec [Tagged k s b]
Real a => Real (Tagged k s a) Source
Methods toRational :: Tagged k s a -> Rational
RealFloat a => RealFloat (Tagged k s a) Source
Methods floatRadix :: Tagged k s a -> Integer floatDigits :: Tagged k s a -> Int floatRange :: Tagged k s a -> (Int, Int) decodeFloat :: Tagged k s a -> (Integer, Int) encodeFloat :: Integer -> Int -> Tagged k s a exponent :: Tagged k s a -> Int significand :: Tagged k s a -> Tagged k s a scaleFloat :: Int -> Tagged k s a -> Tagged k s a isNaN :: Tagged k s a -> Bool isInfinite :: Tagged k s a -> Bool isDenormalized :: Tagged k s a -> Bool isNegativeZero :: Tagged k s a -> Bool isIEEE :: Tagged k s a -> Bool atan2 :: Tagged k s a -> Tagged k s a -> Tagged k s a
RealFrac a => RealFrac (Tagged k s a) Source
Methods properFraction :: Integral b => Tagged k s a -> (b, Tagged k s a) truncate :: Integral b => Tagged k s a -> b round :: Integral b => Tagged k s a -> b ceiling :: Integral b => Tagged k s a -> b floor :: Integral b => Tagged k s a -> b
Show b => Show (Tagged k s b) Source
Methods showsPrec :: Int -> Tagged k s b -> ShowS show :: Tagged k s b -> String showList :: [Tagged k s b] -> ShowS
Ix b => Ix (Tagged k s b) Source
Methods range :: (Tagged k s b, Tagged k s b) -> [Tagged k s b] index :: (Tagged k s b, Tagged k s b) -> Tagged k s b -> Int unsafeIndex :: (Tagged k s b, Tagged k s b) -> Tagged k s b -> Int inRange :: (Tagged k s b, Tagged k s b) -> Tagged k s b -> Bool rangeSize :: (Tagged k s b, Tagged k s b) -> Int unsafeRangeSize :: (Tagged k s b, Tagged k s b) -> Int
Generic (Tagged k s b) Source
Associated Types type Rep (Tagged k s b) :: * -> * Methods from :: Tagged k s b -> Rep (Tagged k s b) x to :: Rep (Tagged k s b) x -> Tagged k s b
Monoid a => Monoid (Tagged k s a) Source
Methods mempty :: Tagged k s a mappend :: Tagged k s a -> Tagged k s a -> Tagged k s a mconcat :: [Tagged k s a] -> Tagged k s a
NFData b => NFData (Tagged k s b) Source
Methods rnf :: Tagged k s b -> ()
type Rep1 (Tagged k s) Source
type Rep (Tagged k s b) Source

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

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 Source

Alias for unTagged

tagSelf :: a -> Tagged a a Source

Tag a value with its own type.

untagSelf :: Tagged a a -> a Source

untagSelf is a type-restricted version of untag.

asTaggedTypeOf :: s -> tagged s b -> s Source

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 Source

Conversion

proxy :: Tagged s a -> proxy s -> a Source

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

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

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

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

Another way to convert a proxy to a tag.

Proxy methods GHC dropped

reproxy :: proxy a -> Proxy b Source

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