[Solved] Using fuctions in C

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If you simply want to call the IsRectangle() function, just add the following code between the next: and } lines:

if (IsRectangle(x1, y1, x2, y2, x3, y3, x4, y4))
{
  printf("The points define a rectangle.\n");
}
else
{
  printf("The points do NOT define a rectangle.\n");
}

However, as others have pointed out, there are a few other problems with your code:

  • There is no return statement in your main() function – it should return an int as specifed in the declaration. More specifically, it should return zero to indicate that the program ended without problems.
  • The goto statements aren’t doing anything to protect against invalid entries. The else code sections will cause printf("Invalid Entry\n"); to be triggered, but the code will then continue on to the next section anyway. Also, GOTO statements make Edsger W. Dijkstra sad.
  • You’ve got almost the exact same code copy-pasted four times, one for each point.

I’d recommend re-factoring your “point input” code into a for loop, with the x/y values stored in arrays for simplicity:

#include <stdio.h>

int main(int argc, char *argv[])
{

    int x[4];
    int y[4];
    int i;

    for (i = 0; i < 4; ++i)
    {
        printf("Please enter point %d: ", i+1);
        while (scanf("%d %d", &x[i], &y[i]) != 2)
        {
            printf("Invalid point, try again: ");
            while (getchar() != '\n') { /* Wait until RETURN is pressed. */ }
        }
    }

    return 0;

}

Alternatively, you could move the input logic into a separate function that is then called four times by main() to get each point.

solved Using fuctions in C