octal package:sbv

Recognize an octal number. Must have a prefix of the form 0o/0O.

>>> octal
(re.++ (re.union (str.to.re "0o") (str.to.re "0O")) (re.+ (re.range "0" "7")))

>>> prove $ \s -> s `match` octal .=> sAny (.== take 2 s) ["0o", "0O"]
Q.E.D.