Data.Finitary.PackWords

If a type a is Finitary, each inhabitant of a has an index, which can be represented as an unsigned integer, spread across one or more machine words. This unsigned integer will have fixed length (as the number of inhabitants of a is finite). We can use this to derive a Unbox instance, by representing Vector as a large array of machine words. We can also derive a Storable instance similarly.

This is the most efficient encoding of an arbitrary finitary type, both due to the asymptotics of encoding and decoding (logarithmic in Cardinality a with base Cardinality Word) and the fact that word accesses are faster than byte and bit accesses on almost all architectures. Unless you have concerns regarding space, this encoding is a good choice.

Unless your type's cardinality is extremely large (a non-trivial multiple of Cardinality Word), this encoding is wasteful. If your type's cardinality is smaller than that of Word, you should consider Data.Finitary.PackInto instead, as you will have much larger control over space usage at almost no performance penalty.

Documentation

data PackWords (a :: Type)

An opaque wrapper around a, representing each value as a fixed-length array of machine words.

Instances

(Finitary a, 1 <= Cardinality a) => Vector Vector (PackWords a)

Defined in Data.Finitary.PackWords

Methods

basicUnsafeFreeze :: PrimMonad m => Mutable Vector (PrimState m) (PackWords a) -> m (Vector (PackWords a))

basicUnsafeThaw :: PrimMonad m => Vector (PackWords a) -> m (Mutable Vector (PrimState m) (PackWords a))

basicLength :: Vector (PackWords a) -> Int

basicUnsafeSlice :: Int -> Int -> Vector (PackWords a) -> Vector (PackWords a)

basicUnsafeIndexM :: Monad m => Vector (PackWords a) -> Int -> m (PackWords a)

basicUnsafeCopy :: PrimMonad m => Mutable Vector (PrimState m) (PackWords a) -> Vector (PackWords a) -> m ()

elemseq :: Vector (PackWords a) -> PackWords a -> b -> b

(Finitary a, 1 <= Cardinality a) => MVector MVector (PackWords a)

Defined in Data.Finitary.PackWords

Methods

basicLength :: MVector s (PackWords a) -> Int

basicUnsafeSlice :: Int -> Int -> MVector s (PackWords a) -> MVector s (PackWords a)

basicOverlaps :: MVector s (PackWords a) -> MVector s (PackWords a) -> Bool

basicUnsafeNew :: PrimMonad m => Int -> m (MVector (PrimState m) (PackWords a))

basicInitialize :: PrimMonad m => MVector (PrimState m) (PackWords a) -> m ()

basicUnsafeReplicate :: PrimMonad m => Int -> PackWords a -> m (MVector (PrimState m) (PackWords a))

basicUnsafeRead :: PrimMonad m => MVector (PrimState m) (PackWords a) -> Int -> m (PackWords a)

basicUnsafeWrite :: PrimMonad m => MVector (PrimState m) (PackWords a) -> Int -> PackWords a -> m ()

basicClear :: PrimMonad m => MVector (PrimState m) (PackWords a) -> m ()

basicSet :: PrimMonad m => MVector (PrimState m) (PackWords a) -> PackWords a -> m ()

basicUnsafeCopy :: PrimMonad m => MVector (PrimState m) (PackWords a) -> MVector (PrimState m) (PackWords a) -> m ()

basicUnsafeMove :: PrimMonad m => MVector (PrimState m) (PackWords a) -> MVector (PrimState m) (PackWords a) -> m ()

basicUnsafeGrow :: PrimMonad m => MVector (PrimState m) (PackWords a) -> Int -> m (MVector (PrimState m) (PackWords a))

(Finitary a, 1 <= Cardinality a) => Bounded (PackWords a)

Defined in Data.Finitary.PackWords

Methods

minBound :: PackWords a

maxBound :: PackWords a

Eq (PackWords a)

Defined in Data.Finitary.PackWords

Methods

(==) :: PackWords a -> PackWords a -> Bool

(/=) :: PackWords a -> PackWords a -> Bool

Ord (PackWords a)

Defined in Data.Finitary.PackWords

Methods

compare :: PackWords a -> PackWords a -> Ordering

(<) :: PackWords a -> PackWords a -> Bool

(<=) :: PackWords a -> PackWords a -> Bool

(>) :: PackWords a -> PackWords a -> Bool

(>=) :: PackWords a -> PackWords a -> Bool

max :: PackWords a -> PackWords a -> PackWords a

min :: PackWords a -> PackWords a -> PackWords a

Show (PackWords a)

Defined in Data.Finitary.PackWords

Methods

showsPrec :: Int -> PackWords a -> ShowS

show :: PackWords a -> String

showList :: [PackWords a] -> ShowS

(Finitary a, 1 <= Cardinality a) => Storable (PackWords a)

Defined in Data.Finitary.PackWords

Methods

sizeOf :: PackWords a -> Int

alignment :: PackWords a -> Int

peekElemOff :: Ptr (PackWords a) -> Int -> IO (PackWords a)

pokeElemOff :: Ptr (PackWords a) -> Int -> PackWords a -> IO ()

peekByteOff :: Ptr b -> Int -> IO (PackWords a)

pokeByteOff :: Ptr b -> Int -> PackWords a -> IO ()

peek :: Ptr (PackWords a) -> IO (PackWords a)

poke :: Ptr (PackWords a) -> PackWords a -> IO ()

Binary (PackWords a)

Defined in Data.Finitary.PackWords

Methods

put :: PackWords a -> Put

get :: Get (PackWords a)

putList :: [PackWords a] -> Put

NFData (PackWords a)

Defined in Data.Finitary.PackWords

Methods

rnf :: PackWords a -> ()

(Finitary a, 1 <= Cardinality a) => Finitary (PackWords a)

Defined in Data.Finitary.PackWords

Associated Types

type Cardinality (PackWords a) :: Nat

Methods

fromFinite :: Finite (Cardinality (PackWords a)) -> PackWords a

toFinite :: PackWords a -> Finite (Cardinality (PackWords a))

start :: PackWords a

end :: PackWords a

previous :: Alternative f => PackWords a -> f (PackWords a)

next :: Alternative f => PackWords a -> f (PackWords a)

Hashable (PackWords a)

Defined in Data.Finitary.PackWords

Methods

hashWithSalt :: Int -> PackWords a -> Int

hash :: PackWords a -> Int

(Finitary a, 1 <= Cardinality a) => Unbox (PackWords a)

Defined in Data.Finitary.PackWords

newtype MVector s (PackWords a)

Defined in Data.Finitary.PackWords

newtype MVector s (PackWords a) = MV_PackWords (MVector s Word)

newtype Vector (PackWords a)

Defined in Data.Finitary.PackWords

newtype Vector (PackWords a) = V_PackWords (Vector Word)

type Cardinality (PackWords a)

Defined in Data.Finitary.PackWords

type Cardinality (PackWords a) = Cardinality a

pattern Packed :: forall (a :: Type). (Finitary a, 1 <= Cardinality a) => a -> PackWords a

To provide (something that resembles a) data constructor for PackWords, we provide the following pattern. It can be used like any other data constructor:

import Data.Finitary.PackWords

anInt :: PackWords Int
anInt = Packed 10

isPackedEven :: PackWords Int -> Bool
isPackedEven (Packed x) = even x

Every pattern match, and data constructor call, performs a \(\Theta(\log_{\texttt{Cardinality Word}}(\texttt{Cardinality a}))\) encoding or decoding of a. Use with this in mind.