Suppose we want to parse a 24-bit hex color value:

input :: ByteString

input = "af093c blah blah blah"

type Color = (Word8, Word8, Word8)

Attoparsec.Char8 exports a nice hexadecimal parser, but it consumes all available hex-flavored input. I'd like to make it consume exactly two bytes, so I could write my color parser like this:

color :: Parser Color

color = do

    r <- hex2

    g <- hex2

    b <- hex2

    return $ Color (r, g, b)

hex2 :: Parser Word8

hex2 = ???

So my question is "how do I write hex2?" I could easily rewrite hexadecimal, but it would be nicer to reuse its hex-handling logic.