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#include <stdio.h>
 
class Method {
    public:    
    virtual void Rum();
};
class Euler : public Method {
    virtual void Rum() {
        printf("ahoj\n");
    }    
};
class Kutta : public Method {
    virtual void Rum() {
        printf("ahoj2\n");
    }    
};
class Simulator {
    public:
    Method *pointer;
    Simulator();
    void setmethod(Method* m) { pointer = m; }
};
 
int main() {
    Simulator s ;
    s.setmethod(new Kutta());
    s.pointer->Rum();
    s.setmethod(new Euler());
    s.pointer->Rum();
}

/home/wWTHI5/cclXxbEJ.o: In function `main':
prog.cpp:(.text+0x16): undefined reference to `Simulator::Simulator()'
/home/wWTHI5/cclXxbEJ.o:(.rodata._ZTI5Kutta[typeinfo for Kutta]+0x8): undefined reference to `typeinfo for Method'
/home/wWTHI5/cclXxbEJ.o:(.rodata._ZTI5Euler[typeinfo for Euler]+0x8): undefined reference to `typeinfo for Method'
collect2: ld returned 1 exit status

Standard output is empty