CODEWITHSUNDEEP
c++templatesinheritancestack
Wayne Hsu
Wayne Hsu

Reputation: 61

C++ Inheriting Stack with Elements with Own Class

I am trying to create my own class (NodeWithMin) as elements for stack in C++, and create a new class (StackWithMin) inheriting it. I think i am ok creating the new stack class, but having some problem initialize a new instance of the new class and use it. Does anybody have a good idea with it? I wrote all classes and main in a single file. Thanks.

#include <stack>

class NodeWithMin{
public:
    int value;
    int min;
    NodeWithMin(int v, int min){
        this->value = v;
        this->min = min;
    }
};

template<class NodeWithMin>
class StackWithMin : stack<NodeWithMin>{
public:
    typedef stack<NodeWithMin> super;
    void push(int value){
        int newMin = min(value, this->min());
        super::push(new NodeWithMin(value, newMin));
    };

    int min(){
        if(this->isEmpty()){
            return numeric_limits<int>::max();
        }else{
            super::peek().min;
        }
    };
};

int main(int argc, const char * argv[])
{
    StackWithMin<class NodeWithMin>* ss;
    ss = new StackWithMin<class NodeWithMin>();
}

Upvotes: 5

Views: 135

Answers (2)

user1508519
user1508519

Reputation:

First off, I removed

using namespace std;

So I can qualify std to remove ambiguities.

The first problem I noticed is this line:

int newMin = min(value, this->min());

My guess is you're trying to use min from algorithm (since stack does not contain a min function):

#include <algorithm>
// snip
int newMin = std::min(value, this->min())

The second problem is you have no instance of stack<NodeWithMin>, only a typedef. Therefore you need to use it like this:

        typedef std::stack<NodeWithMin> super;
        super super_instance;
        void push(int value){
                int newMin = std::min(value, this->min());
                // Why are you using new? It would make
                // It more difficult to avoid memory leaks
                super_instance.push({value, newMin});
        };

The third problem is stack has no member function called isEmpty, and neither does your class. stack doesn't have a peek member function either.

        int min(){
                if(super_instance.empty()){
                        return std::numeric_limits<int>::max();
                }else{
                        return super_instance.top().min;
                }
        };

Now it will compile:

int main(int argc, const char * argv[])
{
    StackWithMin<class NodeWithMin>* ss;
    ss = new StackWithMin<class NodeWithMin>();
    ss->push(42);
    delete ss;
}

I did not bother checking for logic errors.

Upvotes: 2

rajenpandit
rajenpandit

Reputation: 1361

#include <stack>
#include <limits>
using namespace std;
class NodeWithMin{
    public:
            int value;
            int min;
            NodeWithMin(int v, int min){
                    this->value = v;
                    this->min = min;
            }
};

template<class NodeWithMin>
class StackWithMin : stack<NodeWithMin>{
    public:
            typedef stack<NodeWithMin> super;
            void push(int value){
                    int newMin = min(value, this->min());
                    super::push(new NodeWithMin(value, newMin));
            };

            int min(){
                    if(this->isEmpty()){
                            return numeric_limits<int>::max();
                    }else{
                            super::peek().min;
                    }
            };
};

int main(int argc, const char * argv[])
{
    StackWithMin<class NodeWithMin>* ss;
    ss = new StackWithMin<class NodeWithMin>();
}

Please check this code segment, you had missed using namespace std and you will have to include #include <limits> to use numeric_limits<int>::max(); function.

Upvotes: 1

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