problem with simple function

Question

I wana define a simple function in my program so I added this prototype in .h file:

      double TimeCalculation (Ptr <Node> mynode,Ptr <Node> nb_node, Ptr <Ipv4> nbipv4, Ptr <Ipv4> myipv4 );

then i wrote this function:

    double
    TimeCalculation (Ptr <Node> mynode, Ptr <Node> nb_node, Ptr <Ipv4> nbipv4, Ptr <Ipv4> myipv4)
    {
                float cpx,expx,myexpx;
                float cpy,expy,myexpy;
                float cpz,expz,myexpz;
                Vector3D cPosition;
                double itspeed;
    /////////// finding current position and exposition for my current neighbor
                cPosition = nbipv4->GetObject<MobilityModel> ()->GetPosition ();
                cpx = nbipv4->GetObject<MobilityModel> ()->GetPosition ().x;
                cpy = nbipv4->GetObject<MobilityModel> ()->GetPosition ().y;
                cpz = nbipv4->GetObject<MobilityModel> ()->GetPosition ().z;
                expx = nb_node->exPosition.at(0);
                expy = nb_node->exPosition.at(1);
                expz = nb_node->exPosition.at(2);
                itspeed = nbipv4->GetObject<ConstantSpeedPropagationDelayModel> ()->GetSpeed ();
                Vector3D normit(0.0,0.0,0.0),mycPosition;
               //Ptr <Node> mynode;
               // Ptr <Node> nb_node;  
                //v1
                //Vector myexposition = Ipv4->GetObject<Node> ()->GetmyPosition ();
                float normitx= cpx - expx;
                float normity= cpy - expy;
                float normitz= cpz - expz; 
                float itVnorm = sqrt((normitx * normitx) + (normity * normity)+(normitz * normitz)); 

                //hamide:update the amount of exposition to current position
                //pos.insert( it2 ,cPosition); 
                nb_node->exPosition.at(0) = cPosition.x;
                nb_node->exPosition.at(1) = cPosition.y;
                nb_node->exPosition.at(2) = cPosition.z;
                //for calculating v2
                //finding exposition for my node which is calculating MPR set
                myexpx = mynode->exPosition.at(0);
                myexpy = mynode->exPosition.at(1);
                myexpz = mynode->exPosition.at(2);
                mycPosition.x = myipv4->GetObject<MobilityModel> ()->GetPosition ().x; 
                mycPosition.y = myipv4->GetObject<MobilityModel> ()->GetPosition ().y; 
                mycPosition.z = myipv4->GetObject<MobilityModel> ()->GetPosition ().z; 
                double mycpx = myipv4->GetObject<MobilityModel> ()->GetPosition ().x;
                double mycpy = myipv4->GetObject<MobilityModel> ()->GetPosition ().y;
                double mycpz = myipv4->GetObject<MobilityModel> ()->GetPosition ().z;         
                //Vector norm(0.0,0.0,0.0);
                double normx= mycpx - myexpx;
                double normy= mycpy - myexpy;
                double normz= mycpz - myexpz;
                //myexPosition.at(1) = mycPosition.at(1);
                //myexPosition.at(2) = mycPosition.at(2);
                //myexPosition.at(3) = mycPosition.at(3); 
                mynode->exPosition.at(0) = mycPosition.x;
                mynode->exPosition.at(1) = mycPosition.y;
                mynode->exPosition.at(2) = mycPosition.z;          
                double myVnorm = sqrt((normx * normx)+(normy * normy)+(normz * normz));

                //v1*v2
                float entmulti = ((normitx * normx) + (normity * normy) + (normitz * normz));
                // calculating cos for the angel between two vectors for two nodes
                float cos = (entmulti /(itVnorm * myVnorm));
                //the maximum distance a node can see its neighbor its based on the 
                //settings we choose for our topology and simulation condition
                int R = 220;
                //v is the speed of each node
                double myspeed = myipv4->GetObject<ConstantSpeedPropagationDelayModel> ()->GetSpeed ();

                double Td = (R * R)/((myspeed *myspeed)+(itspeed * itspeed)-(2 * itspeed * myspeed*cos));
                return sqrt(Td);

    }

but when i run my program It has this error:

debug/libns3.so: undefined reference to `ns3::olsr::RoutingProtocol::TimeCalculation(ns3::Ptr<ns3::Node>, ns3::Ptr<ns3::Node>, ns3::Ptr<ns3::Ipv4>, ns3::Ptr<ns3::Ipv4>)'
collect2: ld returned 1 exit status

and also IT has a problem which it doesn't work perfect, I will be totally thankful if someone help me with this error and also if u find any other problem in my code.

Answer 1

In general, you cannot define function-template bodies in source files if you want them to be used by other source files. The compiler needs to be able to see the template definition in order to instantiate the code.

The solution is to define the function-template body in the header file.

Answer 2

Apparently you forgot to link some library binaries. With gcc, you can specify libraries to link using the -l-option.