HELP ON INVALID OPERANTS!!!

[ilovepie10]

This is my program:

#include <iostream>
#include <math.h>
using namespace std;

int main() {
    double n, i;   // Declaring variable i and n 
    bool is_prime = true; // Boolean flag; assume true until proven otherwise

    cout << "Enter a number and press ENTER: ";
    cin >> n;

    for (i = 2.0; i <= sqrt(n); i++)    // Test for prime by checking for divisibility by all whole numbers from 2 to sqrt(n).

    {if (n % i == 0.0) 
    bool is_prime = false;}

    if (is_prime = true) {
        cout << "Number is prime." << endl;
    }
    else {
        cout << "Number is not prime." << endl;
    }
    system("PAUSE");
    return 0;
    }

It is to show weather a number is prime or not.

On line 14:

{if (n % i == 0.0)

it says it is an invalid operant to types 'double and 'double'.

Please help, do I have to declare i or n as a float, int, long float, long
int, or long double? DAMNIT!!!

[Jim Pattee]

You can't use the modulo operator '%' on doubles, it can only be used on
integers.

[Jim Pattee]

Take a look at fmod from the math library.

[ilovepie10]

So do I have to include fmod?

[ilovepie10]

Dev-C++ won't let me declared n as an int though, so what do I do?

[ilovepie10]

Thanks jimp03, I changed the code tho this:

#include <iostream>
#include <math.h>
#include <cmath>
using namespace std;

int main() {
    double n, i;   // Declaring variable i and n 
    bool is_prime = true; // Boolean flag; assume true until proven otherwise

    cout << "Enter a number and press ENTER: ";
    cin >> n;

    for (i = 2.0; i <= sqrt(n); i++);    // Test for prime by checking for divisibility by all whole numbers from 2 to sqrt(n).

    if fmod(n/i) == 0; { 
    is_prime = false;
    }

    if (is_prime = true) {
        cout << "Number is prime." << endl;
    }
    else {
        cout << "Number is not prime." << endl;
    }
    system("PAUSE");
    return 0;
    }

to have line 15

if fmod(n/i) == 0; {
[code]
have a parse error before '(' token, so now its easier to fix, though I still don't know how. Please help!