关于c ++：递增和递减运算符重载

increment and decrement operator overloading

下面是我一直在努力解决的问题：

Define a class named PrimeNumber that stores a prime number. The default constructor should set the prime number to 1. Add another constructor that allows the caller to set the prime number. Also, add a function to get the prime number. Finally, overload the prefix and postfix ++ and -- operators so they return a PrimeNumber object that is the next largest prime number (for ++) and the next smallest prime number (for --). For example, if the object's prime number is set to 13, then invoking ++ should return a PrimeNumber object whose prime number is set to 17. Create an appropriate test program for the class.

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#include <iostream>
#include <cstdlib>
using namespace std;

class PrimeNumber
{
public:
PrimeNumber() : pNum(1) {}
PrimeNumber(int setNum) : pNum(setNum) {}
int getNum() const { return pNum; }
PrimeNumber operator ++(); //prefix
PrimeNumber operator ++(int ignoreMe); //postfix
PrimeNumber operator --();
PrimeNumber operator --(int ignoreMe);
bool isPrime(const int& num);
private:
int pNum;
};

int main( )
{
int x;
cout <<"enter prime number =>";
cin >> x;

PrimeNumber p(x);
PrimeNumber hold = p++;
cout <<"Value of hold =>" << hold.getNum() << endl;
cout <<"Value of p =>" << p.getNum() << endl;

cout <<"enter prime number =>";
cin >> x;

PrimeNumber p2(x);
PrimeNumber hold2 = ++p2;
cout <<"Value of hold2 =>" << hold2.getNum() << endl;
cout <<"Value of p2 =>" << p2.getNum() << endl;

cout <<"enter prime number =>";
cin >> x;

PrimeNumber p3(x);
PrimeNumber hold3 = p3--;
cout <<"Value of hold3 =>" << hold3.getNum() << endl;
cout <<"Value of p3 =>" << p3.getNum() << endl;

cout <<"enter prime number =>";
cin >> x;

PrimeNumber p4(x);
PrimeNumber hold4 = --p4;
cout <<"Value of hold4 =>" << hold4.getNum() << endl;
cout <<"Value of p4 =>" << p4.getNum() << endl;

return 0;
}
bool PrimeNumber::isPrime(const int& num)
{
if (num < 2)
{
return false;
}
else if (num == 2)
{
return true;
}
else
{
for (int i = 2; i <= num / 2; i++)
{
if (num % i == 0)
{
return false;
}
}
}
return true;
}

PrimeNumber PrimeNumber::operator ++() //prefix
{
pNum += 1;
while (!isPrime(pNum))
{
pNum++;
}
return pNum;
}
PrimeNumber PrimeNumber::operator ++(int ignoreMe) //postfix
{
int temp = pNum += 1;
while (!isPrime(pNum))
{
temp = pNum;
pNum++;
}
return temp;
}
PrimeNumber PrimeNumber::operator --() //prefix
{
pNum -= 1;
while (!isPrime(pNum))
{
pNum--;
}
return pNum;
}
PrimeNumber PrimeNumber::operator --(int ignoreMe) //postfix
{
int temp = pNum -= 1;
while (!isPrime(pNum))
{
temp = pNum;
pNum--;
}
return temp;
}

此问题与递减运算符重载有关。我认为增量运算符按预期工作。如果没有，请说明。但是，对于固定后的递增和递减操作，hold值似乎不像预期的那样。如何解决问题。此外，如果还有其他可纠正的错误，请注明。

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Output Expected Output
---------- -------------------
enter prime number => 11 enter prime number => 11
Value of hold => 12 Value of hold => 11
Value of p => 13 Value of p => 13
enter prime number => 11 enter prime number => 11
Value of hold2 => 13 Value of hold2 => 13
Value of p2 => 13 Value of p2 => 13
enter prime number => 11 enter prime number => 11
Value of hold3 => 8 Value of hold3 => 11
Value of p3 => 7 Value of p3 => 7
enter prime number => 11 enter prime number => 11
Value of hold4 => 7 Value of hold4 => 7
Value of p4 => 7 Value of p4 => 7