CODEWITHSUNDEEP
c++operator-overloadingpriority-queue
KOB
KOB

Reputation: 4545

Operator overloader not making an affect

I am attempting to create a class that takes a priority queue and reverses the priorities. I include a bool operator<() function as a member function of the class, but no matter how I structure this function, the operator never seems to be overloaded.

Here is my class:

template<typename T>
class MinPQ{

public:

    bool empty() const {
        return pq.empty();
    }

    unsigned int size() const {
        return pq.size();
    }

    void push(const T& element){
        pq.push(element);
    }

    const T& min() const {
        return pq.top();
    }

    void remove_min(){
        pq.pop();
    }

    bool operator<(const T& element) const {
        return pq < element;
    }

private:

    priority_queue<T> pq;
};

EDIT

I also tried changing the overloading function to the following and do not undertsand why that isn't working either.

bool operator<(const T& element){
    return this < element;
}

Upvotes: 0

Views: 72

Answers (1)

AlexStepanov
AlexStepanov

Reputation: 481

Your operator< is meaningless. The only thing it can do is comparing MinPQ<T> object with T object. If you want to compare two T objects you should do this:

1) If the template type T can take only a handful of types, you can write comparison operators explicitly for each of these types:

bool operator<(const T& lhs, const T& rhs)
{
    return lhs > rhs;
}

note: each operator< should be a non-member function. Or a member function of class T with a single argument.

2) write a comparison functor:

template <class T> struct CompareT
{
    bool operator()(const T& lhs, const T& rhs) const
    {
        return lhs > rhs;
    }
};

and then declare pq member as follows:

priority_queue<T, std::vector<T>, CompareT<T>> mq;

3) If you want simply to inverse priorities, you could simply use std::greater class:

priority_queue<T, std::vector<T>, std::greater<T>> mq;

Upvotes: 1

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