unable to overload virtual function - c++

Question

I have a Network class, which I want two virtual functions which I am going to overload: airtime() and airtime(std::vector<int> freq_bins);
I define the class, and the functions at the bottom:
class Network
{
public:
// Properties of the network protocol
std::string _name;
std::vector<float> _channels;
float _bandwidth;
float _txtime;
// Properties of the specific network
int _id;
macs::mac_t _mac;
protocols::protocol_t _protocol;
bool _static;
float _desired_airtime;
float _act_airtime;
bool _active;
// Constructor
Network();
virtual float airtime() { };
virtual float airtime(std::vector<int> freq_bins) { };
};
Now, I have a second class which I want to overload them. Here is the header of this class:
#ifndef _CSMA_H_
#define _CSMA_H_
#include <string>
#include <vector>
#include <map>
#include "MACs.h"
#include "Protocols.h"
#include "Network.h"
class CSMA : public Network
{
public:
float center_freq;
CSMA();
float airtime();
float airtime(std::vector<int> freq_bins);
};
#endif
I then define them in CSMA.cpp:
#include <iostream>
#include <string>
#include <vector>
#include "MACs.h"
#include "Protocols.h"
#include "Network.h"
#include "Simulator.h"
#include "CSMA.h"
extern Simulator sim;
CSMA::CSMA() {
_mac = macs::CSMA;
}
float CSMA::airtime() {
return _act_airtime;
}
float CSMA::airtime(std::vector<int> freq_bins) {
return 1;
}
I get the warning on returning values, that's not a problem. But the errors I get when trying to compile this, I don't understand:
g++ -o hce_sim hce_sim.cpp Network.cpp CSMA.cpp -Wall
In file included from hce_sim.cpp:2:
Network.h:54: error: ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’ cannot be overloaded
Network.h:49: error: with ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’
Network.h: In member function ‘virtual float Network::airtime()’:
Network.h:53: warning: no return statement in function returning non-void
Network.h: In member function ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’:
Network.h:54: warning: no return statement in function returning non-void
In file included from Network.cpp:6:
Network.h:54: error: ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’ cannot be overloaded
Network.h:49: error: with ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’
Network.h: In member function ‘virtual float Network::airtime()’:
Network.h:53: warning: no return statement in function returning non-void
Network.h: In member function ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’:
Network.h:54: warning: no return statement in function returning non-void
In file included from CSMA.cpp:6:
Network.h:54: error: ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’ cannot be overloaded
Network.h:49: error: with ‘virtual float Network::airtime(std::vector<int, std::allocator<int> >)’
I created a more simplified program to try and understand why I get this error, yet this simplified program works:
#include <iostream>
#include <vector>
class Base {
public:
Base() { }
virtual void check() { }
virtual void check(bool it) { }
};
class First : public Base {
public:
First() { }
void check() {
std::cout << "You are in check(void) !\n";
}
void check(bool it) {
std::cout << "You are in check(bool) !\n";
}
};
int main() {
First f;
f.check();
f.check(true);
}
Does anyone have any insight here?

Answer 1

Try pure virtual function declarations.
virtual float airtime() = 0;
virtual float airtime(std::vector<int> freq_bins) = 0;
The reason it fails is that you definitions are incorrect, they don't return anything even though you have specified that it should return float.
Tip: You really shouldn't expose the internal state of your class like that. Do some googling on encapsulation.