How would I use EOF to end input in the following code?

Question

I am currently working on a computer science project and I am stuck whilst trying to work on the final steps. It is very messy thus far, but the code basically takes the first two values given as x and y coordinates, and uses these to produce a total distance. It also then uses a third point to calculate the total uphill and downhill gradients. I have gotten these parts working correctly, however the assignment states: You should read data using scanf until EOF occurs, which can be detected by checking the return value of scanf. I am wondering how I would go about achieving this? At the moment I have the constraints of my do-while loop being that once it = EOF it will terminate, however this causes the code to terminate at any -1 present. Here is the code:

   #include <stdio.h>
#include <math.h>
#include <stdlib.h>

int main(void)
{
    double a;
    double total;
    double up;
    double b;
    double c;
    double d;
    double down;
    double zc;
    double yes;
    double m;
    double n;
    double m2;
    double n2;
    double o;
    double p;
    double q;
    double xc;
    double yc;
    int i = 1;
    xc = 1000;
    yc = 1000;
    total = 0;
    down = 0;
    scanf("%lf", &c);
    do 
    {
        if (i == 1) {
            a = c;
            scanf ("%lf", &c);
            i += 1;
        }
        else if (i == 2) {
            b = c;
            scanf ("%lf", &c);
            i += 1;
        }

        else if (i ==3) {
            d = c;
            if (xc == 1000 && yc == 1000) {
                i = 4;
            }
            else if (xc != 1000) {
                i = 5;
            }
        }


        else if (i == 4) {
                if (d > zc) {
                    yes = d - zc;
                    up = yes/p;
                    if (up > total) {
                        total = up;
                    }
            }
                if (d < zc) {
                    yes = d - zc;
                    up = yes/p;
                     if (up < 0) {
                        up = up *-1;
                    }
                    if (up > down) {
                        down = up;

            }
        }
            xc = b;
            yc = a;
            zc = d;
            scanf ("%lf", &c);
            i = 1;
        }

        else if (i == 5) {
            m = (xc - b);
            n = (yc - a);
            m2 = m*m;
            n2 = n*n;
            o = m2 + n2;
            p = sqrt(o);
            q = q + p;
            i = 4;
        }
    }

    while (c != EOF && i <= 5);


    printf ("Total distance: %.1lf\n", q);
    printf ("Maximum uphill gradient: %.3lf\n", total);
    printf ("Maximum downhill gradient: %.3lf\n", down);
    return EXIT_SUCCESS;
}

And given the following input:

0.0 0.0 0.0
0.0 3.0 1.0
1.0 3.0 2.0
1.0 5.0 -1.0
4.0 5.0 -1.0

Should return:

Total distance: 9.0
Maximum uphill gradient: 1.000
Maximum downhill gradient: 1.500

Answer 1

You can check the function scanf()'s return value. For example: scanf("%d %d",&a,&b); .

1. If read a and b successfully, it will return 2.
2. If only read a successfully, it will return 1.
3. If read 'a' failed,now b is irrelative, for example: a not an int, it will return 0.
4. If get the end of the file while scanf(), it will return EOF.

I hope this can help you.

Answer 2

You can store the return value of scanf like this check=scanf("%lf", &c); And while(check != EOF && i <= 5); The type of check variable must be int.