
  -spec list_to_integer(String, Base) -> integer()
                           when String :: string(), Base :: 2..36.

  Returns an integer whose text representation in base Base is 
  String, for example:

    > list_to_integer("3FF", 16).
    1023

    > list_to_integer("+3FF", 16).
    1023

    > list_to_integer("3ff", 16).
    1023

    > list_to_integer("3fF", 16).
    1023

    > list_to_integer("-3FF", 16).
    -1023

  For example, when Base is 16, String must match the regular
  expression "^[+-]?([0-9]|[A-F]|[a-f])+$".

  Failure: badarg if String contains a bad representation of an
  integer.
