Thread: Function with no argument but return val - throwing up erroneous results

I'm trying to write a function to calculate diameter, circumference and area of circle whereby the function has no argument but has return value. The diameter is coming up fine but circumference and circle area results are way off and the results are also equal to each other! Is there something wrong with my variable declaration or elsewhere? Thanks!

ps: also getting the exactly same wrong results when I'm trying to tackle the same problem through a function with no return val but with an argument.

Code:

#include<stdio.h>


int radius();


int main()


{
    int num;
    
    num = radius();
    
    printf("Diameter is %d\n", num * 2); 
    
    printf("Circumference is %d\n", 2 * 3.14 * num); 
    
    printf("Area is %d\n", 3.14 * num * num); 
}


int radius()


{    int x; 
    
    printf("Enter the radius: ");
    
    scanf("%d", &x);
    
    return x; 
}

Code:

$ gcc main.c -Wall -Werror
main.c: In function ‘main’:
main.c:17:5: error: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘double’ [-Werror=format]
main.c:19:5: error: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘double’ [-Werror=format]
main.c:20:1: error: control reaches end of non-void function [-Werror=return-type]

Perhaps try working with doubles instead of ints.

Hello the problem is that when you multiply 3.14 (PI) then the number you obtain is a float and you are trying to print a float as a regular integer and that's why it's failing.

Code:

printf("Circumference is %d\n", 2 * 3.14 * num);
printf("Area is %d\n", 3.14 * num * num);

change them to handle floats

Thank you, its working but the result is showing up in scientific notation after I've rounded down the float to 2 decimal places using printf("...%.2E"), etc.

Circumference is: 2.512000E+001
Area is: 5.024000E+001

So now my question is how do I convert the scientific notation back to floating point notation? Many thanks,

Just use %f instead of %e.

Many thanks for all your helps.