Data.Monoid.Instances.ByteString.UTF8

This module defines the ByteStringUTF8 newtype wrapper around ByteString, together with its TextualMonoid instance. The FactorialMonoid instance of a wrapped ByteStringUTF8 value differs from the original ByteString: the prime factors of the original value are its bytes, and for the wrapped value the prime factors are its valid UTF8 byte sequences. The following example session demonstrates the relationship:

> let utf8@(ByteStringUTF8 bs) = fromString "E=mc\xb2"
> bs
"E=mc\194\178"
> factors bs
["E","=","m","c","\194","\178"]
> utf8
"E=mc²"
> factors utf8
["E","=","m","c","²"]

The TextualMonoid instance follows the same logic, but it also decodes all valid UTF8 sequences into characters. Any invalid UTF8 byte sequence from the original ByteString is preserved as a single prime factor:

> let utf8'@(ByteStringUTF8 bs') = ByteStringUTF8 (Data.ByteString.map pred bs)
> bs'
"D<lb\193\177"
> factors bs'
["D","<","l","b","\193","\177"]
> utf8'
"D<lb\[193,177]"
> factors utf8'
["D","<","l","b","\[193,177]"]

Documentation

newtype ByteStringUTF8

Constructors

ByteStringUTF8 ByteString

Instances

Eq ByteStringUTF8

Ord ByteStringUTF8

Show ByteStringUTF8

IsString ByteStringUTF8

Monoid ByteStringUTF8

PositiveMonoid ByteStringUTF8

MonoidNull ByteStringUTF8

FactorialMonoid ByteStringUTF8

LeftGCDMonoid ByteStringUTF8

LeftCancellativeMonoid ByteStringUTF8

LeftReductiveMonoid ByteStringUTF8

TextualMonoid ByteStringUTF8

decode :: ByteString -> (ByteStringUTF8, ByteString)

Takes a raw ByteString chunk and returns a pair of ByteStringUTF8 decoding the prefix of the chunk and the remaining suffix that is either null or contains the incomplete last character of the chunk.