/*
 * example of working with strings (pointer version)
 */
#include <stdio.h>
#include <ctype.h>

/* function to count number of letters and digits in a string */
void foobar(char *s, int *num_letters, int *num_digits) {
    /* 
     * local variables for counts
     * we could compute directly into *num_letters and *num_digits but
     * it seems less cumbersome to use local variables 
     */
	int count_l = 0;
	int count_d = 0;
	while (*s != '\0') {
		if (isalpha(*s)) ++count_l;
		if (isdigit(*s)) ++count_d;
		++s;
	}
	*num_letters = count_l;
	*num_digits = count_d;
}

/* function to call foobar and print input, outputs */
void testit(char s[]) {
    int letters;
    int digits;
    foobar(s, &letters, &digits);
    printf("'%s' has %d letters and %d digits\n", s, letters, digits);
}

/* main program with some simple tests */
int main(void) {
    testit("hello1234");
    testit("a 1 b 2 !@#$");
	return 0;
}