char *lowerCase(char *str) {
	char *cp;   // input string cursor
	char *op;   // output string cursor
	char *out;  // output string buffer
	
	out = (char *)malloc(strlen(str)+1);
	assert(out != NULL);
	op = out;
	for (cp = str; *cp != '\0'; cp++) {
		*op = tolower(*cp);
		op++;
	}
	*op = '\0';
	return out;  // what is the precise effect?
}