c - Count number of digits after `.` in floating point numbers?

Question

This is one interview question. How do you compute the number of digit after . in floating point number.

e.g. if given 3.554 output=3

for 43.000 output=0. My code snippet is here

double no =3.44;
int count =0;
while(no!=((int)no))
{
    count++;
    no=no*10;
}
printf("%d",count);

There are some numbers that can not be indicated by float type. for example, there is no 73.487 in float type, the number indicated by float in c is 73.486999999999995 to approximate it.

Now how to solve it as it is going in some infinite loop.

Note : In the IEEE 754 Specifications, a 32 bit float is divided as 24+7+1 bits. The 7 bits indicate the mantissa.

Answer 1

I doubt this is what you want since the question is asking for something that's not usually meaningful with floating point numbers, but here is the answer:

int digits_after_decimal_point(double x)
{
    int i;
    for (i=0; x!=rint(x); x+=x, i++);
    return i;
}