C++：编写一个程序，当输入“-6.5”时终止

Question

The task is to write a simple program which takes an integer and calculates its factorial if an even number is entered, or checks if the number is prime, if an odd number is entered. The program repeats until the value "-6.5" is entered. I added a condition for the loop to stop when that value is entered but instead i get an infinitely repeating loop of the input prompt when that value (or any other decimal) is entered. Why is this happening?

#include <iostream>
using namespace std;
int main ()
{
    int num;
    do
    {
    int choice;
    int factorial=1;
    int count=0;
    cout<<"Enter a number: \n";
    cin>>num;
    if (num>1)
    {
    cout<<"To calculate factorial, enter an even number\n";
    cout<<"\nTo check if a number is Prime or not, enter an odd number\n";
    cin>>choice;

    {
        if (choice%2==0)
    {
        for (int i=num; i>=1; i--)
    {
        factorial=factorial*i;
    }
        cout<<endl;
        cout<<"The factorial of "<<num <<" equals " <<factorial;
        cout<<endl;

    }
    if (choice%2==1)

    {
    for (int i=2;i<num;i++)
        {
           if (num%i==0)
           {
            ++count;
           }

        }
    if (count==0)
    {
        cout<<endl;
        cout<<num <<" is prime.\n ";
    }
    else if (!(count==0))
    {
        cout<<endl;
        cout<<num <<" is not prime.\n";
    }

    }  
    }   
    }

    }
    while (!(num==-6.5));

} 

Answer 1

As a quick glance all your numbers are ints, which will only hold whole numbers and no decimals.

Start with changing any number that is required to hold a decimal with a double or a float (pick which one is best for your application).

See what happens once you change the numbers.