_CP_ascii is equivalent to the result = ascii(string) BASIC statement.
int _CP_ascii(CPSTR** result, CPSTR* string)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
CPSTR * s = _CP_mkstr("a");
_CP_unix_env();
_CP_ascii(&s,s);
printf("%c\n",*(_CP_SADDR(s)));