C++ 我在xfunction内置类中遇到错误，我不知道该怎么办

我正在创建一个映射数据结构，它使用set来保存对值。我为该程序创建了一个自定义的pair类。我完成了大部分调试，现在在内置的xfunction类中出现了这些错误

错误6错误C2784:“bool std:：operator问题在于：

：二进制<代码>

#ifndef MAP_H_2
#define MAP_H_2
#include <list>
#include <set>
#include <utility>
#include <iterator>
#include <iostream>
#include <string>
using namespace std;

//pair class header
template<typename F, typename S>
class Pair
{
public:
    Pair(const F& a, const S& b);
    Pair();
    F get_first() const;
    S get_second() const;
private:
    F first;
    S second;
};
//pair class definitions
template<typename F, typename S>
inline Pair<F, S>::Pair(const F& a, const S& b):first(a),second(b){}

template<typename F, typename S>
inline Pair<F, S>::Pair()
{
}

template<typename F, typename S>
inline F Pair<F, S>::get_first() const
{
    return first;
}

template<typename F, typename S>
inline S Pair<F, S>::get_second() const
{
    return second;
}
//map header
class map2
{
public:
    map2();
    void at_put(string key, int value);
    Pair<string, int> at(string key);
    bool contain_key(string key);
    int value_of(string key);
    void remove_key(string key);
    void print();

private:
    set<Pair<string, int>> theList;
};

//map definition
map2::map2(){}

void map2::at_put(string key, int value)
{
    bool notThere = true;
    if(contain_key(key))
    {
        notThere = false;
    }
    if(notThere)
    {
        Pair<string, int> thePair(key, value);
        theList.insert(thePair);
    }
}

Pair<string, int> map2::at(string key)
{
    set<Pair<string, int>>::iterator iter = theList.begin();
    Pair<string, int> thePair;
    string temp;
    for(int x = 0; x<theList.size() ; x++)
    {
        thePair = *iter;
        temp = thePair.get_first();
        if(!key.compare(temp))
        {
            return thePair;
        }
        iter++;
    }
    Pair<string, int> noPair = Pair<string, int>("none", -1);
    return noPair;
}

bool map2::contain_key(string key)
{
    set<Pair<string, int>>::iterator iter = theList.begin();
    Pair<string, int> thePair;
    string temp;
    for(int x = 0; x<theList.size() ; x++)
    {
        thePair = *iter;
        temp = thePair.get_first();
        if(!key.compare(temp))
        {
            return true;
        }
        iter++;
    }
    return false;
}

int map2::value_of(string key)
{
    set<Pair<string, int>>::iterator iter = theList.begin();
    Pair<string, int> thePair;
    string temp;
    for(int x = 0; x<theList.size() ; x++)
    {
        thePair = *iter;
        temp = thePair.get_first();
        if(!key.compare(temp))
        {
            return thePair.get_second();
        }
        iter++;
    }
    return NULL;
}

void map2::remove_key(string key)
{
    set<Pair<string, int>>::iterator iter = theList.begin();
    Pair<string, int> thePair;
    string temp;
    for(int x = 0; x<theList.size() ; x++)
    {
        thePair = *iter;
        temp = thePair.get_first();
        if(!key.compare(temp))
        {
            theList.erase(iter);
        }
        iter++;
    }
}

void map2::print()
{
    set<Pair<string, int>>::iterator iter = theList.begin();
    Pair<string, int> thePair;
    string temp;
    int temp2;
    for(int x = 0; x<theList.size() ; x++)
    {
        thePair = *iter;
        temp = thePair.get_first();
        temp2 = thePair.get_second();
        cout << "Key:" << temp << " Value:" << temp2 << "\n";
        iter++;
    }
}

#endif

#include "map2.h"
#include <string>
#include <iostream>

using namespace std;


int main()
{
    map2 theMap;
    theMap.at_put("John", 1000);
    theMap.at_put("Chris", 1000);
    theMap.at_put("John", 1500);
    theMap.at_put("Bob", 1250);

    theMap.print();

    theMap.remove_key("bob");

    theMap.print();

    string findKey;
    cout << "please enter a key to remove" << "\n";
    cin >> findKey;

    bool keyFound = theMap.contain_key(findKey);

    if(keyFound)
    {
        cout << "We found it! The value is:" << theMap.value_of(findKey) << "\n";
    }
    else
    {
        cout << "we don’t have this key " << findKey << "in the map" << "\n";
    }


}