[Adot2the]

Writing a program to return a simple true or false for prime numbers. Here's my code, I don't know why it won't work.

// Project 4 IsPrime.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <stdlib.h>
#include <conio.h>
#include <math.h>



#define TRUE 1
#define FALSE 0


void main(void)
{   void isprime ( int );
	
	int x;
	
	
	 
	

	printf ( "Please enter one integer --> ");
	scanf ( "%d", &x );

	isprime( x );
	printf ( "%d" , x);


	 
		
		


   

}



int isprime(int k) 
{	int i;
	int p=0;
	int r;
	

	for (i=2;i<k;i++)
	
	{ r = k % i;
		if (r==0)
		{
			p++;
			
		}

	}
	
	if ( (p==0) )// makes it prime
			return TRUE;
	else
		return FALSE;
}

Could use help, thank you.



-Adot2the

This post has been edited by Adot2the: 04 May 2008 - 12:59 PM

[gabehabe]

The problem is the use of your function. I have corrected your code, take a look and it should become clear.

#include "stdafx.h"
#include <iostream>
#include <stdlib.h>
#include <conio.h>
#include <math.h>



#define TRUE 1
#define FALSE 0

// declare it here
// RETURN A BOOL! (true/false value!)
bool isprime ( int );

int main()
{
    int x;

    printf ( "Please enter one integer --> ");
    scanf ( "%d", &x );

    // call it here
    printf ( "%d" , isprime(x));

    system("pause");
    return EXIT_SUCCESS;
}

// define it here
bool isprime(int k)
{    
    int i;
    int p=0;
    int r;

    for (i=2;i<k;i++)
    { 
        r = k % i;
        if (r==0)
            p++;
    }

    if ( (p==0) )// makes it prime
        return TRUE;
    else
        return FALSE;
}

Basically, you can have your function return a bool, which only has true/false values. Also, you have to declare it before your main function, not inside it. Also, main should return an int, not void

Oh, and when writing stuff like this:

if (condition)
{ code
    code
    more code
}

Try not to write it on the same line as { it just looks ugly

if (condition)
{
    code
    code
    more code
}

Doesn't that look better?

Hope this helps

This post has been edited by gabehabe: 04 May 2008 - 01:42 PM

[Adot2the]

Nice! Thank you so much gabehabe

So making bool functions will only let them return true or false? Woo! I never knew what that meant!

And yea... I always miss those little ugly bodies lol, but I shall get better!