Thread: Checking Input Buffer...

ok so i got a question... again lol big suprise

ok so heres the code i got so far

Code:

//Written By : Andrew Bomstad
//"Day6"

#include<iostream>
#include<ctype.h>

#define cls system("cls");
#define pause system("pause");

using namespace std;

int main()
{
    
    int input;
    cout << "enter a digit" << endl;
    cin>>input;
    cout<<cin;
    pause;
    if(cin){
            cls;
            cout << "You Entered The Number: " << input<<endl;
            pause;
            cls;
            main();
            }
         else{
               cls;
               cout << "Error! Must Enter A Number" << endl;
               pause;
               main();}
         
    pause;
    main();

}

ok... the next part i have NO idea how to go about....
i want a way to send a error message out, if the user inputs more than one input... like say if they type "3hgh" or somthing i want an error message

so im thinkin... do i need to check the keyboard buffer to see how much input was enterd and then do somthing bout that? i dont know really im confused with it all lol

anyhelp would be great guys

o yeah... im also looking for a way to get out of the Infinite loop you'll get if you hit a "Char" in my program. lol i tried clearing the buffer before sending it back to main.. but it just keeps erroring

ok wait no..... now i see my problem...if you type "6tk" it'll still just pick up the 6 and ignore the other two... i want it to error if it picks up any "garbage" input like that

yeah the while loop cleans it up quite a bit,

Code:

//Written By : Andrew Bomstad
//"Day6"

#include<iostream>
#include<ctype.h>

#define cls system("cls");
#define pause system("pause");

using namespace std;

int main()
{
    cls
    int input;
    cout << "enter a digit : ";
    cin>>input;
    while(!cin)
    {
     cls
     cin.clear();
     cin.ignore();
     cout<<"Please enter a number: ";
     cin>>input;
     }

     cout<<"You entered the number "<<input<<endl;
     pause
     main();

}

but it still allows the user to hit "6gh" and sill still pick up the int value, i want it to void the user's input if they hit Chars at All

I'm not sure that's possible, and if it is, I don't know how to do it. I don't think you can look ahead in the input buffer.

ok, then the next step is to not input int, but input strings insteads, this way you won't get the failing stream on char inputs and you'll be able to test the whole input before passing it on.

Code:

//Written By : Andrew Bomstad and Darryl :-)
//"Day6"

#include <iostream>
#include <cctype> // prefer cctype over ctype.h
#include <string> 

#define cls system("cls");
#define pause system("pause"); // ok for newbie but ditch it with experience

using namespace std;

int main()
{
	while (true)
	{
		cls
			string input; // c++ strings are your friend.
		bool valid_input;
		do
		{
			cout << "enter a digit : ";
			cin >> input;
			// don't need the cin check now
			for (int i = 0; i <input.size();++i)
			{
				valid_input = true;
				if (!isdigit(input[i]))
				{
					cout<<"Error: Non-numeric data entered\n";
					valid_input = false;
					break;
				}
			}
		}while (!valid_input);

		cout<<"You entered the number "<<input<<endl;
		pause
	}
}

Hey Thanks Alot Darryl, Thats Exactly What I was after, i was just getting to using isdigit() but i couldnt get that stomped out, but again thanks for the help!

hey i got one more question, i just need to figure out whats going on, in the "isdigit(); statement, like i said ive been trying to figure it out latley and obviously you know whats going on

Originally Posted by AndyBomstad

hey i got one more question, i just need to figure out whats going on, in the "isdigit(); statement, like i said ive been trying to figure it out latley and obviously you know whats going on

isdigit() takes a char as its parameter and determines if that is a digit and return true if it is and false if it's not. I imagine it just does a simple test if (char > '0' && char < '9' )

Since we were working with strings I had to loop through the string checking each char 1 at a time. In a string using the index operator[] will return a single char for that position.

string test = "12345A";
cout << test[2] ; //outputs '3'
cout << isdigits( test[5]); // outputs false, but cout will convert to 0;

I was thinking of using atoi() but it still would have converted a string like "65dfs" to just 65