fmod problem

How to use fmod inside a if function?

Code:

---

double List ()
{
  double Div = N;

  while (--Div > 0){

    if((N % Div) == 0 )
    printf("%.lf +", Div);
  }
}

---

Quote:

---

Originally posted by yusiye
How to use fmod inside a if function?

Code:

---

double List ()
{
  double Div = N;

  while (--Div > 0){

    if((N % Div) == 0 )
    printf("%.lf +", Div);
  }
}

---

---

I changed to

Code:

---

double List ()
{
  double Div = N;
  d = fmod(Div, N);
  while (--Div > 0){

    if( d == 0 )

    printf("%.lf +", Div);

  }
}

---

But I got overflow, please help:confused: :confused:

fmod returns the remainder of a divisor and dividend presented by the code. It is a very useful tool, but you need to remember that floats and doubles are not always exact, so you might not get the desired result.

The code you have presented

Code:

---

double List ()
{
  double Div = N;

  while (--Div > 0){

    if((N % Div) == 0 )
    printf("%.lf +", Div);
  }
}

---

appears to attempt to use modulo vice fmod. You could either use fmod:

Code:

---

if((fmod(N,Div))==0)

---

or cast your doubles into ints and use modulo:

Code:

---

if(((int)N % (int)Div)) == 0)

---

Your choice.

What's it supposed to do?

When comparing floating-point values to an exact value such as zero, you need to remember that floating-point is an approximation and it's best to test for "close enough" instead of exactly the same.

C provides the FLT_EPSILON, DBL_EPSILON, and LDBL_EPSILON macros in float.h for such use.

-Prelude