How to convert negative zero to positive zero in C?

Question

Hello I'm learning Objective C and I was doing the classic Calculator example.

Problem is that I'm getting a negative zero when I multiply zero by any negative number, and I put the result into a (double) type!

To see what was going on, I played with the debugger and this is what I got:

(gdb) print -2*0
$1 = 0

(gdb) print (double) -2 * 0
$2 = -0

In the second case when I cast it to a double type, it turns into negative zero! How can I fix that in my application? I need to work with doubles. How can I fix the result so I get a zero when the result should be zero?

Answer 1

I did a simple test:

double d = (double) -2.0 * 0;

if (d < 0)
    printf("d is less than zero\n");
if (d == 0)
    printf("d is equal to zero\n");
if (d > 0)
    printf("d is greater than zero\n");

printf("d is: %lf\n", d);

It outputs:

d is equal to zero
d is: -0.000000

So, to fix this, you can add a simple if-check to your application:

if (d == 0) d = 0;