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.

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.