Thread: 'cin' and 'scanf()' issue

I just started learning C++ lately and im experiencing the same problems of 'scanf()' with 'cin' (well i consider them as problems).

'cin' doesn't read characters it can't , and leaves them in the stream just like 'scanf()' with the newline character for example , but i can get rid of the '\n' with no problems so i don't care much about that.

What i care about is , in the following program :

Code:

...
int num;
while(1)
{
   cout << "Enter a number : ";
   cin >> num;

   if(num == -1) break;
}
...

if i enter any character instead of a number , the program would loop infinitely at that point and "Enter a number : " would be all over the screen !!

I'm guessing that when cin\scanf() can't read a character it leaves it in the input stream , then at the next attempt it would try to read it again but still can't and so on... am i guessing right? if not , then whats causing the problem?

cin's >> operator has the same problems as scanf, and your guesses are correct.

sorry i forgot to ask why this wouldn't eat the characters left in the stream like it does with the newline character (ch is 'char'):

Code:

...
cin >> integer;
ch = cin.get();  // this is suppoed to eat the first character left there
...

but the program skips the second line as if cin.get() reads the '\n' first , even with multiple variables with cin.get() they would be all skipped.

Why did that happen and how would i clear the stream from ANY character(s) left in there?


thanks for the replying Prelude

>// this is suppoed to eat the first character left there
It would if the stream weren't in an error state. Use cin.clear() before trying to read and discard unwanted characters.

k thanks alot man