Problem writing to file

First of all, hello, I'm new here.

I have been trying to hack together a number tester, which will test a number to see if it's a prime or not. It should write the result to a file, but it doesn't. I've also been trying to figure out the source of the problem, but I just don't get it.

Here it is, to it's fullest:

Code:

---

// The program should test a number, defined by user-input, if it's a prime number or not.
// This through dividing each number below the user-inputted, starting from 2
// to, let the user-input be k, k-1. If all cases return a remainder, the number first inputted
// number is a prime.
// If none of the cases have a remainder the number is not a prime.

#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;



int main ()       
{
int true_false, quit;
float i, k, result;
result = fmod(k, i);
i = 2;               
cin >> k;

ofstream primefile;
primefile.open ("Primeer.txt", ios::ate);

if (!primefile.is_open())
{
    cout << " The file could not be opened. ";
    }
    else
    {

while (i = k - 1)     
{
result = fmod(k,i);   
   
 if (result = 0)             
 {                           
          true_false = true_false + 1;   
          break;
          cout << " The following number isn't a prime: " << k;
          primefile << " The following number isn't a prime: " << k;
          primefile.close();
          cout << " Succesfull writing to file: " << primefile;
          } 
         
 if (result > 0)
 {
          true_false = true_false + 0;
          i++;
          }                                 

              }
                }
 
 
 
                   
if (i = k - 1, true_false = 0)
{
      cout << " The following number is a prime: " << k;
      primefile << " The following number is a prime: " << k;
      cout << " Succesfull writing to file: " << primefile; 
          }


             
cin >> quit;           
if (quit == true)     
 {                     
        return 0;     
        }


}

---

Hope I didn't screw the formatting up.

Any help would be appreciated.

Quote:

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Originally Posted by Imagine

Code:

---

while (i = k - 1)     
// ...
if (result = 0)             
// ...   
if (i = k - 1, true_false = 0)
// ...

---

---

Is this really what you meant?

Well, what's the error(s)?

What do you mean Jimzy? I think I made a mistake, it should be:

Code:

---

while ( i<k )
{
  //...
}

---

The problem I'm having is that the program doesn't output any data, whatsoever.

= is assignment, == is test for equality. For example,

Code:

---

if (result = 0) {

---

means set the value of result to 0 and never execute the code block, since the value of the expression "result = 0" is 0, which evaluates to false.

As robatino explained.
By assigning 0 to result, this

Code:

---

if (result = 0)
{
  // ...
}

---

won't be true, and code inside this if won't execute. Same story goes for:

Code:

---

if (result > 0)  // result is 0 after previous assignment

---

and

Code:

---

if (i = k - 1, true_false = 0)

---

Just fix ifs conditions and it should help.

Thanks very for pointing that out. Forgot about that.