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How to trap an error

Posted on 2002-03-17
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Last Modified: 2010-04-02
Hi,

I have declared a variable as integer and i make some calculations based on the user input..I have taken care of negative numbers but how to trap if the user enters anything other than a number...

here is the sample code which i have used..

cout << "Choose a option of your choice: \n";
cin >> selection;


     if (!cin)
          cerr << "Invalid selection \n";
     else
     if (selection<0)
          cout << " You have entered a negative selection " << amount << "\n";
     else
     if  (selection>5)
          cout << " Invalid selection: " << amount << "\n";

Thanks

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Question by:sramkris
6 Comments
 
LVL 12

Expert Comment

by:lexxwern
ID: 6875963
what you're doing is okay but i just sweetened it a bit with some modifications.

if (!cin || selection<0 || selection>5)
   cout << "ERROR:Invalid Selection \n";
0
 
LVL 1

Author Comment

by:sramkris
ID: 6876114
Hi

This still does not work...If i enter a alphabet or any other key apart from a number it just scrolls or rather hangs...IT does not solve the problem...Is there any way i can force the user to only use numbers...

Thanks
0
 
LVL 3

Expert Comment

by:job_s
ID: 6876191
If Ur using Getchar() U can verify the input by checking the char between 48 - 57

:gch
char ch= Getchar()
if( ch<48 && ch > 57 )
   GoTo gch;

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LVL 2

Expert Comment

by:gurpreets
ID: 6876451
The only way you can check for invalid inputs is by taking char input and converting it to int if it is valid.
0
 
LVL 1

Expert Comment

by:Shivshankar
ID: 6876685
It works very well in my compiler.
Could you pls tell what compiler do u use ?
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LVL 12

Accepted Solution

by:
lexxwern earned 400 total points
ID: 6877116
char ch= Getchar()
if( !(ch<48 && ch > 57) )
{

         cout << " You have entered a negative selection " << amount << "\n";
}

this should do it or you.


lhn
0

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