[Haskell-cafe] Attoparsec.ByteString.Char8 or Attoparsec.ByteString for diff output?

[Viktor Dukhovni]

On Mon, Feb 20, 2023 at 10:46:38AM -0400, Pedro B. wrote:

> Thanks Li-yao . As I mentioned in my answer to Viktor, I am now using 
> the ByteString functions except when I want to parse Char8's, for 
> example to parse an 'a' with Data.Attoparsec.ByteString.Char8.char 'a'.

FWIW, you can often avoid the Char8 combinators, e.g. for matching a
specific 8-bit (ASCII) character, at a modest loss of readability,
you can just match its Word8 code point:

    0x0a <--- '\n'
    0x0d <--- '\r'
    0x20 <--- ' '
    0x30 <--- '0'
    0x41 <--- 'A'
    0x61 <--- 'a'
    ...

I am comfortable with the raw hex values of various "interesting"
characters, but you can also define aliases:

    import Data.Char (ord)

    char_nl, char_cr, char_sp, char_0, char_A, char_a :: Word8
    char_nl = fromIntegral $ ord '\n'
    char_cr = fromIntegral $ ord '\r'
    char_sp = fromIntegral $ ord ' '
    ...

-- 
    Viktor.