Question

I’ve written a small program but the answer it gives is always wrong, here is the code

double radiusc;
double xcenter;
double ycenter;

bool onthecircle(int x,int y);


int main(void)
{
    int inputwait;

    printf("Please enter x coordinate of your center point: ");
    scanf("%d",&xcenter);

    printf("Please enter y coordinate of your center point: ");
    scanf("%d",&ycenter);

    printf("Please enter the radius of the circle: ");
    scanf("%d",&radiusc);

    double left_x = xcenter - radiusc;
    double left_y = ycenter;

    double down_x = xcenter;
    double down_y = ycenter - radiusc;

    if(left_x >= floor(left_x))
    {
        left_x = floor(left_x);
        int (left_x);
    }
    else
    {
        left_x = floor(left_x) + 1;
        int (left_x);
    }

    for(left_x; left_x<=xcenter; left_x++)
    {
        for(left_y;left_y>ycenter-radiusc;left_y--)
        {
            if(onthecircle(left_x,left_y))
                printf("Jest na kole: %d , %d \n", left_x,left_y);
        }
    }

    scanf("%i",&inputwait);

    return 0;
}

bool onthecircle(int x,int y)
{
    double t1= x - xcenter;
    double t2 = x - ycenter;

    if ((t1*t1 + t2*t2) > (0,9 *radiusc*radiusc) &&
        (t1*t1 + t2*t2) < (1,1 *radiusc*radiusc))
        return 1;
    else
        return 0;

}

When I debug, typing 0,0 as my center and r = 1, it gives me the point 0, and some big number, instead of saving 1 as the value for r, it gets a random huge number, and I have no idea why. Any ideas?

Answer 1

In addition to the problem Ed found, 0,9 is not a valid floating-point constant; you want 0.9. (Locale settings can affect input and output representations; they don’t affect language syntax.)

The comma in (0,9 *radiusc*radiusc) is a comma operator, not a decimal point; you’re multiplying the square of the radius by 9.

And you’re missing the #include <stdio.h> and #include <math.h> (for floor() at the top of your program (your compiler might let you get away with that, but it’s not optional).

And the format in your printf calls is incorrect; you need "%f" or "%g" for `double’.

More:

Your use of a double as a loop control variable is questionable. The call scanf("%i",&inputwait); to wait for input before terminating the program without a prompt is user-hostile. There is no need to use global variables. I don’t know what int (left_x); is supposed to do; I think it’s parsed as a declaration (of a variable that you never use), and the parentheses are superfluous. Your use of the type name bool means either that you’re compiling your code as C++, or that you have either a #include <stdbool.h> or a definition of bool that you haven’t bothered to show us.

That’s about as much debugging as I’m willing to do for now. Fix these errors and try again.