重载运算符以允许 qsort 在C++中工作

我用C++写了一段代码，然后决定将其更改为面向对象和除qsort工作之外的所有函数。我已经查找了它与运算符重载有关，但我不知道该怎么做。有人可以帮忙吗？

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;
class OpAmps {
private:
    char Name[20]; 
    unsigned int PinCount; 
    double SlewRate; 
public:
    void Enter(OpAmps&, unsigned long&);
    void Save(const OpAmps*, unsigned long);
    void Load(OpAmps*, unsigned long&);
    void Sort(OpAmps*, unsigned long);
    int SortName(const void*, const void*);
    int SortSlewRate(const void*, const void*);
    void Display(const OpAmps*, unsigned long);
};
#define DATABASE_MAX 10
#define DATABASE_FILENAME "database.txt"
int main()
{
    OpAmps OpAmp[DATABASE_MAX]; 
    OpAmps Menu;
    unsigned long database_length = 0; 
    char UserInput;
    while (1) {
        cout << endl;
        cout << "Op-amp database menu" << endl;
        cout << "--------------------" << endl;
        cout << "1. Enter a new op-amp into the database" << endl;
        cout << "2. Save the database to disk" << endl;
        cout << "3. Load the database from disk" << endl;
        cout << "4. Sort the database" << endl;
        cout << "5. Display the database" << endl;
        cout << "6. Exit from the program" << endl << endl;
        cout << "Enter your option: ";
        cin >> UserInput;
        cout << endl;
        switch(UserInput) {
            case '1':
            Menu.Enter(OpAmp[database_length], database_length);
            break;
            case '2':
            Menu.Save(OpAmp, database_length);
            break;
            case '3':
            Menu.Load(OpAmp, database_length);
            break;
            case '4':
            Menu.Sort(OpAmp, database_length);
            break;
            case '5':
            Menu.Display(OpAmp, database_length);
            break;
            case '6':
            return 0;
            default:
            cout << "Invalid entry" << endl << endl;
            break;
        }
    }
}
void OpAmps::Enter(OpAmps& Op, unsigned long& length)
{
    if (length == DATABASE_MAX) {
        cout << "The database is full" << endl;
    }
    else {
        cout << "Add new data" << endl;
        cout << "------------" << endl;
        cout << "Enter op-amp name: ";
        cin >> Op.Name;
        cout << "Enter number of pins: ";
        cin >> Op.PinCount;
        cout << "Enter slew rate: ";
        cin >> Op.SlewRate;
        cout << endl;
        length++;
    }
}
void OpAmps::Save(const OpAmps* Op, unsigned long length)
{
    fstream output_file;
    output_file.open(DATABASE_FILENAME, ios::out);
    if(output_file.good()) {
        output_file << length << endl << endl;
        for (unsigned long i=0;i<length;i++) {
            output_file << Op[i].Name << endl;
            output_file << Op[i].PinCount << endl;
            output_file << Op[i].SlewRate << endl << endl;
        }
    }
    output_file.close();
}
void OpAmps::Load(OpAmps* Op, unsigned long& length)
{
    fstream input_file; 
    input_file.open(DATABASE_FILENAME, ios::in);
    if(input_file.good()) {
        input_file >> length;
        for (unsigned long i=0;i<length;i++) {
            input_file >> Op[i].Name;
            input_file >> Op[i].PinCount;
            input_file >> Op[i].SlewRate;
        }
    }
    input_file.close();
}
void OpAmps::Sort(OpAmps* Op, unsigned long length)
{
    char UserInput;
    cout << endl;
    cout << "Sorting options" << endl;
    cout << "---------------" << endl;
    cout << "1. To sort by name" << endl;
    cout << "2. To sort by slew rate" << endl;
    cout << "3. No sorting" << endl << endl;
    cout << "Enter your option: ";
    cin >> UserInput;
    cout << endl;
    switch(UserInput) {
        case '1':
        cout<<"sortName"<<endl;
        qsort(Op,length,sizeof(OpAmps),SortName);
        break;
        case '2':
        cout<<"sortslew"<<endl;
        qsort(Op,length,sizeof(OpAmps),SortSlewRate);
        break;
        case '3':
        return;
        default:
        cout << "Invalid entry" << endl << endl;
        break;
    }
}
int SortName(const void *First, const void* Second)
{
    return strcmp(((OpAmps *) First)->Name, ((OpAmps *) Second)->Name);
}
int SortSlewRate (const void *First, const void* Second)
{
    return (int) ((((OpAmps *) First)->SlewRate > ((OpAmps *) Second)->SlewRate)? 1 : -1);
}
void OpAmps::Display(const OpAmps* Op, unsigned long length)
{
    if (length == 0) {
        cout << "No elements in the database" << endl;
    }
    else {
        cout << endl;
        for (unsigned long i=0;i<length;i++) {
            cout << "Name: " << Op[i].Name <<endl;
            cout << "Number of Pins: " << Op[i].PinCount << endl;
            cout << "Slew Rate: " << Op[i].SlewRate << endl;
            cout << endl;
        }
    }
}

干杯家伙:Dxx