Trouble with a program

[shtuff123]

I'm supposed to make one program that calculates the volume of a cone from the user input of a height and radius. It's also supposed to call a function to do this, and ask if they want to enter another value. If they say "N" it breaks.
I am getting an error that says undefined reference to volumef(). Here's my code
Thanks for any help in advance :D

#include <iostream>
#include <cmath>
#define PI 3.14159
#include <string>
using namespace std;
double volumef();
double vol, radius, height;
string con;

int main ()

{



cout<<"^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^"<<endl;
cout<<" Program by me "<<endl;
cout<<"^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^"<<endl;

while (true)
{
cout<<"Enter a Radius: "<<endl;
cin>>radius;
cout<<"Enter a Height: "<<endl;
cin>>height;
vol=volumef();
cout<<"The volume is "<<vol<<endl;
cout<<" Do you want to enter another value? (Y/N)"<<endl;
cin>>con;
if ("con"=="N")
{
break;
}
}

system("pause");
return 0;
}

double volumef(double radius, double height)
{
double vol;
vol=1/3*PI*radius*radius*height;
return vol;
}
//end function

[Moschops]

In C++, the compiler must know about a function before you try to use it. You can do this in one of two ways:

1) Move your definition of the function in question above the main function.
2) Declare the function ahead of use, with a prototype double volumef(double radius, double height);

You have attempted to do method 2, but you've got the prototype wrong. You used
double volumef(); which is the prototype for a function named volumef that returns a double and takes in no parameters, whereas your actual function volumef takes in two double parameters.

As an aside, if ("con"=="N")? Why are there quote marks around con?

Edit; NinjaTASTIC! :)

[Peter87]

Please put your code inside code tags [code] [/code] to make your code easier to read and increase the your chances to get helped.

double volumef(double, double) is not the same function as double volumef().

[Need4Sleep]

you declare volume having two parameters, but call the function with zero. The compiler takes this as function overloading and looks for a volumef() function with no parameters, which is non-existent.

vol=volumef(); // no parameters 

what it should be:

vol=volumef(radius,height);

[Peter87]

Moschops wrote:

Edit; NinjaTASTIC! :)

Your answer is best so it deserves being first.

[shtuff123]

Thank you for your replies!
The program works now but it is giving me a volume of 0 for any input

[Peter87]

1/3 Both operands are integers so it will do integer division. The result is 0 so the whole expression will also be 0.