C++ Promises

promises.cpp

#include <iostream>
#include <cstdlib>
#include <functional>

template <typename ValueT, typename ReasonT>
class Promise {
private:
    enum State {
        FULFILLED, REJECTED, PENDING
    };

    State mState;
    ValueT value;
    ReasonT reason;

    void setState(State s);
    
public:
    Promise(std::function<void(std::function<Promise<ValueT, ReasonT>> resolve,std::function<Promise<ValueT, ReasonT>> reject)>);
    ~Promise();
};

template <typename ValueT, typename ReasonT>
Promise::Promise(std::function<void(std::function<Promise<ValueT, ReasonT>> resolve,std::function<Promise<ValueT, ReasonT>> reject)>):
    mState(Promise::State::PENDING) {
}

template <typename ValueT, typename ReasonT>
Promise::setState(Promise::State s) {
    mState = s;
}

int main(int argc, char* argv[]) {
    return 0;
}