Flat.Repr

Documentation

>>> :set -XScopedTypeVariables
>>> import Flat.Instances.Base
>>> import Flat.Decoder.Types
>>> import Flat.Types
>>> import Flat.Run
>>> import Flat.Class

newtype Repr a

Flat representation of a value

Repr

It is occasionally useful to keep a decoded value, or part of it, in its encoded binary representation and decode it later on demand.

To do so, just decode a value a to a `Repr a`.

For example, we encode a list of Ints and then decode it to a list of Repr Int:

>>> unflat (flat [1::Int .. 5]) :: Decoded ([Repr Int])
Right [Repr {repr = "\STX\SOH"},Repr {repr = "\EOT\SOH"},Repr {repr = "\ACK\SOH"},Repr {repr = "\b\SOH"},Repr {repr = "\n\SOH"}]

To decode a `Repr a` to an a, we use unrepr:

>>> let Right l = unflat (flat [1..5]) :: Decoded [Repr Int] in unrepr (l  !! 2)
3

See "test/FlatRepr.hs" for a test and a longer example of use.

SizeOf

If a decoded value is not required, it can be skipped completely using `SizeOf a`.

For example, to ignore the second and fourth component of the following tuple, it can be decoded as:

>>> let v = flat ('a',"abc",'z',True) in unflat v :: Decoded (Char,SizeOf String,Char,SizeOf Bool)
Right ('a',SizeOf 28,'z',SizeOf 1)

The unused values have not been decoded and instead their size (in bits) is returned.

Constructors

Repr

Fields

• repr :: ByteString

Instances

Show (Repr a)

Defined in Flat.Repr

Methods

showsPrec :: Int -> Repr a -> ShowS

show :: Repr a -> String

showList :: [Repr a] -> ShowS

Flat a => Flat (Repr a)

Defined in Flat.Repr

Methods

encode :: Repr a -> Encoding

decode :: Get (Repr a)

size :: Repr a -> NumBits -> NumBits

unrepr :: Flat a => Repr a -> a