Thread: Entering valid user input?

  1. #1
    Registered User
    Join Date
    Mar 2013

    Entering valid user input?

    Hello guys; I am wondering if you can help me.
    How can I write my simple program so if the user enters an invalid number,
    The program won’t exit? I know I am supposed to use a if (cin) or if (!cin),
    But I don’t know where in the program or how I should use it. Right now my
    Program looks kind of like this:
    If (number > 1 && number < 1001)
    Go through some function loops
    Cout << “invalid number”;
    I need to write it so when the user enters an invalid number, the program
    Would Keep asking for the right number until it's given.
    Thanks guys.
    Last edited by Frank1234; 03-19-2013 at 07:54 PM.

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    Like so.
    #include <iostream>
    #include <iomanip>
    #include <limits>
    using namespace std;
    int main()
      int var = 0;
      do {
        if ( cin >> var ) {
          if ( var >= 1 && var <= 99 ) {
            cout << "Good" << endl;
          } else if ( var != -1 ) {
            cout << "Out of range" << endl;
        } else {
          cout << "Garbage input" << endl;
      } while ( var != -1 );
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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