_CP_index is equivalent to the result = index(string1, string2, expression) BASIC statement.
int _CP_index(int* result, CPSTR* string1, CPSTR* string2, int expression)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
/* Prints "2". */
CPSTR * s = _CP_mkstr("bbc");
CPSTR * t = _CP_mkstr("b");
int i;
_CP_index(&i,s,t,2);
_CP_unix_env();
printf("%d\n", i);