octal package:tomland

Parse an integer in the octal representation. The format of the octal number is expected to be according to the Haskell report except for the fact that this parser doesn't parse “0o” or “0O” prefix. It is a responsibility of the programmer to parse correct prefix before parsing the number itself. For example you can make it conform to the Haskell report like this:
octal = char '0' >> char' 'o' >> L.octal
Note: before version 6.0.0 the function returned Integer, i.e. it wasn't polymorphic in its return type. Warning: this function does not perform range checks.