Input stream

This is a discussion on Input stream within the C++ Programming forums, part of the General Programming Boards category; Hey everyone, how do I make it so when a user enters a string or character when the program is ...

  1. #1
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    Input stream

    Hey everyone, how do I make it so when a user enters a string or character when the program is waiting for an integer the program doesn't flip out? I currently have something like:
    Code:
    while (n!=-1)
    {
       cin>>n;
    }
    but the program crashes when a letter or string is entered.

  2. #2
    Lead Moderator kermi3's Avatar
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    what is n's decleration?
    Kermi3

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  3. #3
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    Guest
    It's declared as an int

  4. #4
    Evil Member
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    If cin cannot translate what it finds into the appropriate variable, it enters a fail state. You can check for this. Here is some example code:

    Code:
    #include <iostream>
    
    #define expletive "moron"
    
    using namespace std;
    
    int main () {
    
      int n;
    
      bool nisgood = false;
    
      while (!nisgood) {
    
        cin >> n;
    
        if (cin.fail()) {
    
          cout << "That was supposed to be a NUMBER, " << expletive << ", now try again";
    
          //fflush(stdin); // Heh just kidding
    
          while (getchar() != '\n') {}
    
          cin.clear();
    
        } else nisgood = true;
    
      }
    
      return 0;
    
    }
    You can of course make this more elegant by tidying the error checking method into a tighter loop.
    Last edited by Imperito; 11-12-2002 at 07:18 PM.

  5. #5
    moi
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    forgot quotes around moron
    hello, internet!

  6. #6
    Evil Member
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    D'oh.

    It wasn't "moron" when I typed it. Thats the beauty of macros...

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