An integer or a string. The string representation can be decimal,
hexadecimal or octal.
base
The base. Defaults to 0.
The base may vary from 2 to 36. If base is 0 (default value), the
actual base is determined from the leading characters: if the first
two characters are 0x or 0X,
hexadecimal is assumed, otherwise if the first character is "0",
octal is assumed, otherwise decimal is assumed.
Note:
It is not necessary to call this function if you want to use
integer or string in place of GMP number in GMP functions, like
gmp_add(). Function arguments are
automatically converted to GMP numbers, if such conversion is
possible and needed, using the same rules as
gmp_init().