Input Validation for only integers?

[Charles Talbert]

I created a program that will calculate the factorial of the number entered and am having a hard time getting it to not accept decimals or fractions.

#include <iostream>
using namespace std;
int main (){
	
	int number = 0;
		
	cout<<"Please enter a positive whole number:"<<endl;
	while(!(cin>>number)||number<0){
		cin.clear();
		while(cin.get()!='\n'){ /*Also, this was the only thing I could find to stop it from looping Invalid 
                                        //input endlessly but I am not sure exactly what this is doing, if anyone
                                        //could explain that would help alot*/
			continue;
			cin>>number;
		}
		cout<<"Invalid Input"<<endl;
		}
	int x = number;	
	int y=1;
	while(x>1){
		y = y*x;
		x--;
		}
	cout<<y;
	return 0;
}

I am 2 months into my first programming class ever and I cant seem to figure out how to get around the fact that if I enter '3.2' or '3/2' it will only look at the '3' and not the '.2', or '/2'. I would probably need to change the data type to float or something but then I am not sure how to use the input validation after that. I tried using isdigit(number) but that was not working either...and to be honest I may not have been using it right.

I have googled just about everything I could think of but I am not sure where to go. If anyone can point me in the right direction that would help immensely! Thanks!
Chuck

[DSLq5Di1]

Replace your while loop with,

while ((cin >> number).fail() || cin.peek() != '\n' || number < 0)
{
    cin.clear();
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    cout << "Invalid Input\n";
}

[Charles Talbert]

Thanks!
I put in the code above and it didn't work (undeclared numeric_limits), but I was able to add the cin.peek() != '\n' to my while statement and it works now... the only thing is, I have no clue what that does. Can anyone point me to a good place to learn about these cin.clear/peek/get and the like, or if you have the time, explain what they are doing in this loop?

Thanks again,
Chuck

[DSLq5Di1]

Oh sorry, forgot to mention you need #include <limits> .

peek() returns the next character in the stream without extracting it, clear() is used to reset the stream state (ie. if a failed extraction occurs), get() extracts a character from the stream.

See http://www.cplusplus.com/reference/iostream/istream/ for a reference of what you can do with cin.