The _CP_alpha function is equivalent to the result = alpha(string) BASIC statement.
int _CP_alpha(int* result, CPSTR* string)
This function returns -1 if an error occurs. The error code is contained in _CP_errno.
/* is "hi" alphabetic? */
CPSTR * s = _CP_mkstr("hi");
int i;
_CP_alpha(&i,s);
_CP_unix_env();
printf("%d\n", i);
_CP_str_free(s);