[Haskell-beginners] How do you show a Data.ByteArray?

[haskell at verge.info.tm]

Prelude Data.ByteArray> c = Data.ByteArray.zero 20
Prelude Data.ByteArray> :type c
c :: ByteArray ba => ba
Prelude Data.ByteArray> c

<interactive>:38:1: error:
    • Ambiguous type variable ‘a0’ arising from a use of ‘print’

Uhm...

Prelude Data.ByteArray> index c 3

<interactive>:39:1: error:
    • Ambiguous type variable ‘a0’ arising from a use of ‘index’

I can't print a byte?