{-| Match a hexadecimal digit

>>> match hexDigit "1"
"1"
>>> match hexDigit "A"
"A"
>>> match hexDigit "a"
"a"
>>> match hexDigit "g"
""
-}
hexDigit :: Pattern Char
hexDigit = satisfy isHexDigit
hexDigit :: Pattern Char
hexDigit = satisfy isHexDigit
hexDigit = satisfy isHexDigit