/*
  Name:    improved-ex13-5.c
  Purpose: finds the sum of all command line arguments
  Author:  Bill Slough

  Notes:
    1.  Uses strtol(), the preferred approach to convert strings to integer
        values.

    2.  Note that the sum is now accumulated using the long data type.
        
*/

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <stdbool.h>

#define BASE 10              /* assume command line arguments to be base 10 */

bool bad_arg = false;        /* has at least one bad argument been seen? */

void process(long *psum, const char *arg);

int main(int argc, char *argv[ ]) {
    int i;
    long sum;

    /* process each command line argument, skipping the 0th argument */
    i = 1;
    sum = 0;
    while (argv[i] != NULL) {
        process(&sum, argv[i]);
        i++;
    }
    
    /* announce result */
    if (!bad_arg) {
        printf("sum = %ld\n", sum);
        return 0;
    }
    else {
        printf("Errors: no reliable sum available.\n");
        return 1;
    }
}

void process(long *psum, const char *arg) {
    char *ptr;

    /* convert this argument and accumulate the sum */
    *psum += strtol(arg, &ptr, BASE);

    /* did an error occur during conversion? */
    if (*ptr != '\0' || errno == EINVAL || errno == ERANGE) {
        printf("error in command line argument: \"%s\"\n", arg);
        bad_arg = true;
    }
}