Undefined reference to a method in another class file, how to fix? - class

Question

I've been working on a program that will do a couple of equations in regards to audio, SPL, etc.
I decided to have the main class file present the user with an option to choose what equation he wants to do, while the equations are housed in another class file.
Atm, the main class file is setup just to test maxPeakSPL(), yet I can't get it to run.
main.cpp
//Kh[a]os
#include "equations.h"
#include <iostream>
void mainLoop();
int maxSPL = 0;
int main()
{
std::cout << "Created by Kh[a]os" << std::endl << std::endl;
mainLoop();
return 0;
}
void mainLoop()
{
std::cout << "hi";
maxSPL = equations::maxPeakSPL();
std::cout << std::endl << maxSPL << "db" << std::endl << std::endl;
}
equations.h
#ifndef EQUATIONS_H
#define EQUATIONS_H
#include <string>
class equations
{
public:
equations();
static int maxPeakSPL();
protected:
private:
};
#endif // EQUATIONS_H
equations.cpp
#include "equations.h"
#include <iostream>
#include <string>
equations::equations()
{
}
static int maxPeakSPL()
{
int Sens = 0;
double Distance = 0;
int Watts = 0;
int sWatts = 2;
int eWatts = 0;
double maxSPL = 0;
double counter = 0;
double wall = 0;
std::string corner = "";
bool v = true;
std::cout << "Sensitivity (db): " << std::endl;
std::cin >> Sens;
std::cout << "Amplification (watts): " << std::endl;
std::cin >> Watts;
std::cout << "Listening Distance (meters): " << std::endl;
std::cin >> Distance;
std::cout << "Distance from Wall (ft): " << std::endl;
std::cin >> wall;
std::cout << "Are you they in a corner? (y/n): " << std::endl;
std::cin >> corner;
maxSPL = Sens - (Distance*3 - 3);
while(v == true)
{
if (sWatts > Watts)
{
v = false;
eWatts = sWatts;
sWatts = sWatts/2;
Watts = Watts-sWatts;
counter = (double)Watts/(double)eWatts;
counter = counter*3;
maxSPL = maxSPL + counter;
}
if (v == true)
{
maxSPL = maxSPL + 3;
sWatts = sWatts*2;
}
}
if (wall <= 4)
maxSPL = maxSPL + 3;
if (corner == "Y" || corner == "YES" || corner == "y" || corner == "yes")
maxSPL = maxSPL + 3;
return maxSPL;
}
The error I get when I run it is: undefined reference to `equations::maxPeakSPL()'
I haven't a clue how to fix this, any assistance would be great. Thank you.

Answer 1

In your main, try putting the function before the main block. Include an underscore before the name of your directives/flags.