| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Control.Monad.Codec
Description
The Codec monad provides functions for encoding and decoding
complex data structures with unique integer numbers. In the
simplest case the entire sturecture can be transformed to unique
atom (see example1 below). When it is not sufficient to encode
the input object with one codec, more complex codec structure can
be used (see example2 below). The library relies on a 'data-lens'
package which provides types and functions for codec manipulations.
Example:
example1 = evalCodec empty $ do
let xs = "abcabd"
ys <- mapM (encode idLens) xs
zs <- mapM (decode idLens) ys
return $ zip zs ys>>>example1>>>[('a',0),('b',1),('c',2),('a',0),('b',1),('d',3)]
example2 = evalCodec (empty, empty) $ do
let xs = zip "abcabd" [1, 34342, 5435, 34342, 124, 1]
ys <- forM xs $ \(x, y) ->
(,) <$> encode fstLens x <*> encode sndLens y
zs <- forM ys $ \(i, j) ->
(,) <$> decode fstLens i <*> decode sndLens j
return (zs, ys)>>>fst example2>>>[('a',1),('b',34342),('c',5435),('a',34342),('b',124),('d',1)]>>>snd example2>>>[(0,0),(1,1),(2,2),(0,1),(1,3),(3,0)]
Synopsis
- data Codec c a
- data AtomCodec a = AtomCodec {}
- empty :: AtomCodec a
- type AtomLens c a = Lens c (AtomCodec a)
- maybeEncode :: Ord a => AtomLens c a -> a -> Codec c (Maybe Int)
- encode :: Ord a => AtomLens c a -> a -> Codec c Int
- encode' :: Ord a => AtomLens c a -> a -> Codec c Int
- maybeDecode :: Ord a => AtomLens c a -> Int -> Codec c (Maybe a)
- decode :: Ord a => AtomLens c a -> Int -> Codec c a
- runCodec :: c -> Codec c a -> (a, c)
- evalCodec :: c -> Codec c a -> a
- execCodec :: c -> Codec c a -> c
- idLens :: Lens a a
Documentation
A Codec monad preserves mappings between objects and respective codec components.
Atomic Codec component, which represents to and fro mapping
between a objects and unique intergers.
type AtomLens c a = Lens c (AtomCodec a) Source #
Just a type synonym for a lens between codec and codec component.
maybeEncode :: Ord a => AtomLens c a -> a -> Codec c (Maybe Int) Source #
Encode the object with codec component identified by the lens. Return Nothing if the object is not present in the atomic codec component.
encode :: Ord a => AtomLens c a -> a -> Codec c Int Source #
Encode the object with codec component identified by the lens.
encode' :: Ord a => AtomLens c a -> a -> Codec c Int Source #
Version of encode which doesn't update the return componenent of the atom codec. It is useful when we know that particular value (e.g. value of a condition observation) won't be decoded afterwards so there is no need to store it and waste memory.
maybeDecode :: Ord a => AtomLens c a -> Int -> Codec c (Maybe a) Source #
Decode the number with codec component identified by the lens. Return Nothing if the object is not present in the atomic codec component.
decode :: Ord a => AtomLens c a -> Int -> Codec c a Source #
Decode the number with codec component identified by the lens. Report error when the number is not present in the codec component.
runCodec :: c -> Codec c a -> (a, c) Source #
Run the Codec monad with the initial codec value. Return both the result and the final codec state. The obtained codec can be used next to perform subsequent decoding or encoding.
evalCodec :: c -> Codec c a -> a Source #
Evaluate the Codec monad with the initial codec value. Only the monad result will be returned.