Why cant i reject Decimals? (C++) - c++

Question

With this code:
#include <iostream>
#include <iomanip>
using namespace std;
//Functions
int power(int base,int exp);
double energy(int z, int n);
//Main
int main() {
const double E0(13.6),hce(1.24E-6),e(1.6E-19);
int n1,n2,z;
double E;
cout << "**************************************" << endl;
cout << "Welcome to the energy level calculator\n" << endl;
cout << "Please enter the atomic number, z: " << endl;
cin >> z; //Ask for z
cout << "Please enter n for the initial energy level: " << endl;
cin >> n1; //Ask for n1
cout << "Please enter n for the final energy level: " << endl;
cin >> n2; //Ask for n2
while(cin.fail()||z<1||n1<1||n2<1){
cout << "\n\n\n\n\nPlease enter non-zero integers only, try again\n\n\n\n\n\n" << endl;
cout << "**************************************" << endl;
cin.clear();
cin.ignore();
cout << "Please enter the atomic number, z: " << endl;
cin >> z; //Ask for z
cout << "Please enter n for the initial energy level: " << endl;
cin >> n1; //Ask for n1
cout << "Please enter n for the final energy level: " << endl;
cin >> n2; //Ask for n2
}
etc...
The program is only allowed to accept Integers
If i enter a decimal, such as 1.2 the program rejects the 1. but uses the 2 as z when it should be asking for input from the keyboard?
Can anyone help?

Answer 1

Since you asked for an explanation, when you enter 1.2
cin >> z; //Successfully reads '1' into 'z'
cin >> n1; //Fails to read '.' into 'n1'. '.' remains the first character in the stream.
cin >> n2; //Fails to read '.' into 'n2'. '.' remains the first character in the stream.
You then loop back to the beginning of your loop.
cin.clear(); //clears the fail flag from the two previous failed inputs
cin.ignore(); // ignores the '.'
cin >> z; //Reads '2' into 'z'. The stream is now empty.
The program then blocks on cin >> n1 waiting for more characters to be placed in the stream.
After each input, you should see if the input failed.
cin>>n1;
if(cin.fail())
cin.ignore();