我正在实施A *算法来解决几个问题-8个难题问题和另一个问题。对于A Star,我在A_star.hpp中实现了三个通用类:
template <class U>
class Heuristic{
public:
virtual int getHeuristic(Node<U> currNode, Node<U> target);
};
template <class V>
class NextNodeGenerator{
public:
virtual vector<pair<V, int> > generate(Node<V> curr);
};
template <class W>
class CompareVal{
public:
virtual bool compare(W val1, W val2);
};
为了解决8难题问题,我为上述每个通用类在prob2.cpp中实现了三个子类:
template <class hT>
class PuzzleHeuristic: public Heuristic<hT>{
public:
virtual int getHeuristic(Node<hT> currNode, Node<hT> target){
//Code for getHeuristic
}
};
template <class cT>
class PuzzleCompareVal: public CompareVal<cT>{
public:
virtual bool compare(cT val1, cT val2){
//Code for compare
}
};
template <class nT>
class PuzzleNNG: public NextNodeGenerator<nT>{
public:
virtual vector<pair<nT, int> > generate(Node<nT> curr){
//Code for generate
}
在A_star.hpp中,我还有一个AStar类:
template <class Y>
class AStar{
Heuristic<Y> *h;
NextNodeGenerator<Y> *nng;
CompareVal<Y> *comp;
public:
void setHeuristic(Heuristic<Y> *hParam){
h = hParam;
}
void setNNG(NextNodeGenerator<Y> *nngParam){
nng = nngParam;
}
void setCompareVal(CompareVal<Y> *compParam){
comp = compParam;
}
vector<Node<Y> > solve(Y start, Y target){
//Code for solve
}
在prob2.cpp的main()函数中,我创建了一个AStar对象(Array是我单独定义的模板类):
int main()
{
PuzzleHeuristic<Array<int> > pH;
PuzzleCompareVal<Array<int> > pCV;
PuzzleNNG<Array<int> > pNNG;
AStar<Array<int> > aStar;
aStar.setHeuristic(&pH);
aStar.setNNG(&pNNG);
aStar.setCompareVal(&pCV);
vector<Node<Array<int> > > answer = aStar.solve(start, target);
}
编译时,出现以下错误:
/tmp/ccCLm8Gn.o:(.rodata._ZTV17NextNodeGeneratorI5ArrayIiEE[_ZTV17NextNodeGeneratorI5ArrayIiEE]+0x10):未定义对
NextNodeGenerator<Array<int> >::generate(Node<Array<int> >)' /tmp/ccCLm8Gn.o:(.rodata._ZTV10CompareValI5ArrayIiEE[_ZTV10CompareValI5ArrayIiEE]+0x10): undefined reference to
CompareVal> :: compare(Array,Array)'的引用/tmp/ccCLm8Gn.o:(.rodata._ZTV9HeuriEE+] ):未定义对`Heuristic> :: getHeuristic(Node>,Node>)的引用collect2:错误:ld返回1退出状态Blockquote
我怀疑问题是由于模板函数的继承所致。是什么原因引起的错误?
所有虚拟函数都需要一个定义,即使它们在子类中被覆盖也是如此。如果您不想在基类中实现它们,并强制子类重写函数,则应使它们在基类中抽象化,例如
template <class V>
class NextNodeGenerator{
public:
virtual vector<pair<V, int> > generate(Node<V> curr) = 0;
// ^^^^
// This is what makes the function an abstract function
};
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