Something

%%%main.cpp:
#include "astar.h"
int main(int argc, char* argv[])
{
    misstate start={3,3,true,0};
    astar<misstate> a;
}

%%%astar.h:
template <class T>
class astar
{
    void init_s(T s1);
}

%%%astar.cpp:
#include "astar.h"
template <class T>
void astar<T>::init_s(T s1)
{
    s=s1;
}


%%%error:
g++ -g -Wall -o StarSearch astar.o main.o
/usr/bin/ld: Undefined symbols:
astar<misstate>::init_s(misstate)