Parse an integer in the hexadecimal representation. The format of the
hexadecimal number is expected to be according to the Haskell report
except for the fact that this parser doesn't parse “0x” or “0X”
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:
hexadecimal = char '0' >> char' 'x' >> L.hexadecimal
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.