closing while(cin.good()) loop properly - c++

Question

I'm trying to make the program exit properly without it. I have '|' as my exit, if its the first thing I do when first running, it closes fine. But after entering values and printing them, afterwards entering '|' to exit.
It prints out:
"The smaller value is 0
The larger is previous second value" // want to remove this from showing
int main()
{
double first = 0, second = 0;
while(cin.good()){
char exit;
cout << "Enter '|' to exit.\n";
cout << "Enter two numbers:";
cin >> first >> second;
exit = cin.peek();
if(exit=='|'){
break;}
else{
if(first<second){
cout << "\nThe smaller value is " << first << "\nThe larger value is " << second << endl;
}
else if(first>second){
cout << "\nThe smaller value is " << second << "\nThe larger value is " << first << endl;
}
}
}
}

Answer 1

In your code, you've assumed that the input from your users will be limited to something usable as a double. This isn't necessarily the case. The issue that you're running into isn't related to the statement exit = cin.peak(); but to cin >> first >> second; You can test this by entering any non-numerical input into your program and watching it fail by assigning a 0 to the first and leaving second as is.
In short, because the conversion of the input into a double fails, you get an indeterminate value for first and then your program moves on.
You can use the following code as an example. In this, I first populate my variables as strings, then attempt a conversion after the fact.
#include <iostream>
#include <string>
#include <stdlib.h>
using namespace std;
int main()
{
string str_first, str_second;
double first = 0, second = 0;
while(cin.good()){
cout << "Enter '|' to exit.\n";
cout << "Enter two numbers:";
cin >> str_first >> str_second;
if( (str_first.compare("|") == 0) || (str_second.compare("|") == 0) ){
cout << "\nThanks for playing\n" << endl;
break;}
else{
first = strtod (str_first.c_str(), NULL);
second = strtod (str_second.c_str(), NULL);
if(first<second){
cout << "\nFirst is small: The smaller value is " << first << "\nThe larger value is " << second << endl;
}
else if(first>second){
cout << "\nSecond is small: The smaller value is " << second << "\nThe larger value is " << first << endl;
}
}
}
}