'cin' and 'scanf()' issue

This is a discussion on 'cin' and 'scanf()' issue within the C++ Programming forums, part of the General Programming Boards category; I just started learning C++ lately and im experiencing the same problems of 'scanf()' with 'cin' (well i consider them ...

  1. #1
    former member Brain Cell's Avatar
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    '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?
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  2. #2
    Code Goddess Prelude's Avatar
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    cin's >> operator has the same problems as scanf, and your guesses are correct.
    My best code is written with the delete key.

  3. #3
    former member Brain Cell's Avatar
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    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
    Last edited by Brain Cell; 11-07-2004 at 10:14 AM.
    My Tutorials :
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  4. #4
    Code Goddess Prelude's Avatar
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    >// 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.
    My best code is written with the delete key.

  5. #5
    former member Brain Cell's Avatar
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    k thanks alot man
    My Tutorials :
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    (constrcutive criticism is very welcome)


    - Brain Cell

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