C ++错误，而使用< set> [英] C++ Errors while using <set>

问题描述

我保持实例化的错误。尝试修复它，不管是什么，我似乎无法实现SET。尝试使用向量，但我不知道如何正确实现一个等式运算符和失败。

一开始我使用向量，但是很难使用， x和y值是唯一的。意思是，我会读一个数据的文本文件。
Point1，[3，10]
p>



点1将从点2进入不同的向量，然后单独存储数据。但不知何故，在文本文件中有Point1，[3，10]的重复值。我不想插入另一个相同的记录，并希望它们是独一无二的。所以我尝试使用集合，但我不能真正插入数据。

错误是：

在成员函数'bool std :: les <_Tp> :: operator（）（const _Tp& const
_Tp&）const [with _Tp = Point]'：STL_TREE.h：980：实例化从'std :: pair :: iterator，bool> std :: _ Rb_tree< _Key，... STL_SET.h：307：实例化从'std :: pair，_Compare，typename
_Alloc :: rebind< _Key> :: other> :: const_interator，bool> std :: set ..... main.cpp：141：从这里实例化stl_function.h：227：error：no
匹配'operator<'in '_ x _y'

Point.h

  #ifndef POINT_H 
 #define POINT_H 
 
 #include< iostream> 
 #include< ostream> 
 #include< fstream> 
 #include< sstream> 
 #include< vector> 
 #include< math.h> 
 #include< set> 
 #include< string.h> 
 #include< string> 
 #include< stdio.h> 
 
 using namespace std; 
 
 class Point 
 {
 friend ostream& operator<<（ostream& const; const Point&）; 
 
 protected：
 int x，y; 
 
 public：
 // c'tor 
 Point（int xx，int yy）; 
 
 // setters 
 void setX（int x1）; 
 void setY（int y1）; 
 
 // getters 
 int getX（）const {return x;}; 
 int getY（）const {return y;}; 
}; 
 
 Point :: Point（int xx，int yy）：x（xx），y（yy）
 {
 
} 
 $ b b void Point :: setX（int x1）
 {
x = x1; 
} 
 
 void Point :: setY（int y1）
 {
 y = y1; 
} 
 
 #endif 
  

Main.cpp

  #includePoint.h
 #include< iostream> 
 #include< ostream> 
 #include< fstream> 
 #include< sstream> 
 #include< set> 
 #include< math.h> 
 #include< set> 
 #include< string.h> 
 #include< string> 
 #include< stdio.h> 
 #include< map> 
 #include< algorithm> 
 #include< map> 
 
 using namespace std; 
 
 class Main 
 {
 public：
 void mainMenu（）; 
 void stringToUpper（string& s）; 
}; 
 
 void stringToUpper（string& s）
 {
 for（unsigned int l = 0; l< s.length（）; l ++）
 {
s [l] = toupper（s [1]）; 
} 
} 
 
 void Main :: mainMenu（）
 {
 cout<1）类型文件名和读取数据< ; endl; 
 cout<<2）查看数据<< endl; 
 cout<<Q）输入'Q'退出<< endl<< endl; 
} 
 
 int main（）
 {
 Main main; 
 char menuChoice; 
 bool quit = false; 
 int count = 0; 
 
 set< Point> p; 
 
 while（！quit）
 {
 main.mainMenu（）; 
 cout<< 请输入您的选择：; 
 cin>> menuChoice; 
 menuChoice = toupper（menuChoice）; 
 
 switch（menuChoice）
 {
 case'1'：
 {
 string line，name; 
 char filename [50]; 
 int x，y; 
 
 cout<< 请输入文件名：; 
 cin>>文件名; 
 
 ifstream myfile（filename）; 
 if（myfile.is_open（））
 {
 while（myfile.good（））
 {
 getline（myfile，line）; 
 {
 for（unsigned int i = 0; i< line.size（）; ++ i）
 {
 if（line [i] =='[' || line [i] ==']'|| line [i] =='，'）
 {
 line [i] =' 
} 
 istringstream（line）; 
在>> name>> x>> y; 
} 
 if（name ==Point）
 {
 p.insert（Point（x，y））} 
} 
 count ++; 
} 
 myfile.close（）; 
 cout<<计数; 
} 
 else cout<< 无法打开文件; 
} 
 break; 
 case'2'：
 {
 cout<<view data<< endl; 
} 
 case'Q'：
 cout<<你已经选择退出了！<< endl; 
 quit = true; 
 exit（0）; 
 default：
 cout<<Invalid entry<< endl<< endl; 
 break; 
} 
} 
} 
  

解决方案>

如果你想把Point放在一个集合中，那么设置需要一种方法来比较一个Point和另一个Point，这样它就可以按顺序排列。您必须声明此函数

  bool operator<（const Point& p1，const Point& p2）
 {
 ... 
} 
  

这样做就可以实例化 std :: set< Point>

通常的实现是

  bool operator<（const Point& p1，const Point& p2）
 {
 return p1.x& p2.x || p1.x == p2.x&&& p1.y< p2.y; 
} 
  

这个命令并不重要， d可能已经意识到你需要运算符< 更快），只要你遵守 strict weak ordering 的规则。

I kept geting instantiated errors. Try fixing it, no matter what, I can't seem to implement SET. Tried using vectors but I have no idea how to implement an equality operator properly and failed too.

At first I was using vectors but it was hard to use while trying to keep x and y values unique. Meaning, I would read a text file of data. Point1, [3, 10] Point2, [10, 10]

So Point 1 will go to different vector from Point 2 and then storing the data seperately. But somehow, in the text file there are repeat values of Point1, [3, 10]. I do not want to inset another same record and want them to be unique. So i tried using set but I could not really insert in the data.

Errors are:

In member function 'bool std::les<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = Point]': STL_TREE.h:980: instantiated from 'std::pair::iterator, bool> std::_Rb_tree<_Key,.... STL_SET.h:307: instantiated from 'std::pair, _Compare, typename _Alloc::rebind<_Key>::other>::const_interator, bool> std::set..... main.cpp:141: instantiated from here stl_function.h:227: error: no match for 'operator<' in '_x <_y'

Point.h

#ifndef POINT_H
#define POINT_H 

#include <iostream>
#include <ostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <math.h>
#include <set>
#include <string.h>
#include <string>
#include <stdio.h>

using namespace std;

class Point
{
    friend ostream& operator<<(ostream&, const Point&);

    protected:
        int x, y;

    public:
        //c'tor
        Point(int xx, int yy);

        //setters
        void setX(int x1);
        void setY(int y1);

        //getters
        int getX() const {return x;};
        int getY() const {return y;};
};

Point::Point(int xx, int yy) : x(xx), y(yy)
{

}

void Point::setX(int x1)
{
    x=x1;
}

void Point::setY(int y1)
{
    y=y1;
}

#endif

Main.cpp

#include "Point.h"
#include <iostream>
#include <ostream>
#include <fstream>
#include <sstream>
#include <set>
#include <math.h>
#include <set>
#include <string.h>
#include <string>
#include <stdio.h>
#include <map>
#include <algorithm>
#include <map>

using namespace std;

class Main
{
    public: 
        void mainMenu();
        void stringToUpper(string &s);
};

void stringToUpper(string &s)
{
    for(unsigned int l=0; l < s.length(); l++)
    {
        s[l] = toupper(s[l]);    
    }
}

void Main::mainMenu()
{
    cout<<"1)   type filename and read data"<<endl;
    cout<<"2)   View data"<<endl;    
    cout<<"Q)   Enter 'Q' to quit"<<endl<<endl;
}

int main()
{
    Main main;
    char menuChoice;
    bool quit=false;
    int count = 0;

    set<Point> p;

    while ( !quit)
    {
        main.mainMenu();
        cout << "Please enter your choice : ";
        cin>>menuChoice;
        menuChoice = toupper(menuChoice);

        switch(menuChoice)
        {
            case '1':
                {
                    string line, name;
                    char filename[50];
                    int x,y;

                    cout << "Please enter filename : ";
                    cin >> filename;

                    ifstream myfile(filename);
                    if (myfile.is_open())
                    {
                        while ( myfile.good() )
                        {
                            getline(myfile, line);
                            {      
                                for (unsigned int i = 0; i < line.size(); ++i) 
                                {
                                    if (line[i] == '[' || line[i] == ']' || line[i] == ',') 
                                    {
                                        line[i] = ' ';
                                    }
                                    istringstream in(line);
                                    in >> name >> x >> y;                                  
                                }
                                if(name == "Point")
                                {
                                p.insert(Point(x,y))    }                        
                            }                                
                            count++;
                        }    
                        myfile.close();
                        cout << count;
                    }
                    else cout<< "Unable to open file";
                }
                break;                             
            case '2':
                {
                cout<<"view data"<<endl;
                }                   
            case 'Q':
                cout<<"You have chosen to quit!"<<endl;
                quit=true;
                exit(0);
            default:
                cout<<"Invalid entry"<<endl<<endl;
                break;
        }
    }
}

解决方案

If you want to put Point in a set, then set needs a way to compare one Point with another so it can put them in order. You must declare this function

bool operator<(const Point& p1, const Point& p2)
{
    ...
}

Do that and you will be able to instantiate std::set<Point>

The usual implementation would be

bool operator<(const Point& p1, const Point& p2)
{
    return p1.x < p2.x || p1.x == p2.x && p1.y < p2.y;
}

It doesn't really matter what the order is (I assume otherwise you'd have probably realised you needed operator< sooner) as long as you obey the rules of strict weak ordering.

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