C++ Noob question - Overclock.net

kris_cs1 · 06-27-05

Right, I have decided that seeing as though it is the summers hols for me that i will go through my SAMs teach yourself book. I will probably to asking for a lot of help

And here is my first question. Why doesn't this work?

Code:


#include<iostream>
 
usingnamespace std;
 
int main(int argc, char* argv[])
 
{
 
int ReturnCode = 0;
 
float Dividend = 1;
 
cout << "Dividend: ";
 
cin >> Dividend;
 
if (!cin.fail())
 
{
 
float Divisor;
 
cout << "Divisor: ";
 
cin >> Divisor;
 
if (!cin.fail())
 
{
 
float Result = (Dividend/Divisor);
 
cout << Result << endl;
 
}
 
else
 
{
 
cerr << "Input error, not a number?" << endl;
 
cin.clear();
 
char BadInput[5];
 
ReturnCode = 1;
 
};
 
}
 
else
 
{
 
cerr << "Input error, not a number?" << endl;
 
cin.clear();
 
char BadInput[5];
 
ReturnCode = 1;
 
};
 
char StopCharacter;
 
cout << endl << "Press a key and \"Enter\": ";
 
cin >> StopCharacter;
 
return ReturnCode;
 
}

It is copied exactly from the book but the error catching routine doesn't work. It just closes on both Visual C++.net and Dev C++.
Thanks very much
Kris

Melraidin · 06-27-05

Quote:

Originally Posted by kris_cs1

Right, I have decided that seeing as though it is the summers hols for me that i will go through my SAMs teach yourself book. I will probably to asking for a lot of help

And here is my first question. Why doesn't this work?

[snip]

It is copied exactly from the book but the error catching routine doesn't work. It just closes on both Visual C++.net and Dev C++.
Thanks very much
Kris

As far as I can tell the error handler is running fine, except you don't have any form of pause to allow the user to view the error. I imagine either you missed a couple lines copying from the book, or the book needs to be updated (a common occurence, sadly).

Try adding a line such as "cin >> BadInput;" after the BadInput definition in each of the error handlers, this will work just like the StopCharacter lines towards the end; it will allow the user to view the error message and force the user to enter a character before closing the application.

Jonrezz · 06-27-05

try adding this bit of code at the end of your main function:

system("PAUSE");
return EXIT_SUCCESS;

kris_cs1 · 06-27-05

Ah yes of course. I always hated this book lol.
Thanks very much both of you!

kris_cs1 · 06-27-05

Well, I may as well ask so that I understand it.
Why is it that it doesn't stop anyway when running these lines:

Code:

 
cout << endl << "Press a key and \"Enter\": ";
cin >> StopCharacter;

If you put a 'cin >> BadInput' into the else blocks, the "Press a key and \"Enter\": " displays and waits for user input after it. Without the 'cin >> BadInput' however, it does not display. Why is it that it does not stop at 'cin >> StopCharacter;'? without the 'cin >> BadInput' in the else block? Also, why is it that with the 'cin >> BadInput' it seems to skip that and wait for user input in the StopCharacter variable. Surely it should stop and wait for the user to input something into the BadInput variable and then go on to prompting for the user to input a character into the StopCharacter variable, not just skip the first one.... am i making any sense?

Melraidin · 06-27-05

Quote:

Originally Posted by kris_cs1

Well, I may as well ask so that I understand it.
Why is it that it doesn't stop anyway when running these lines:

Code:

 
cout << endl << "Press a key and \"Enter\": ";
cin >> StopCharacter;

If you put a 'cin >> BadInput' into the else blocks, the "Press a key and \"Enter\": " displays and waits for user input after it. Without the 'cin >> BadInput' however, it does not display. Why is it that it does not stop at 'cin >> StopCharacter;'? without the 'cin >> BadInput' in the else block? Surely it shoud stop and wait for the user to input something into the BadInput variable and then go on to prompting for the user to input a character into the StopCharacter variable, not just skip the first one.... am i making any sense?

Haven't got time to test the code, but possibly the input buffer still has the invalid input inside? Try flushing the buffer (I believe it's cin.clear(), but not positive) before each input.

kris_cs1 · 06-27-05

Quote:

Originally Posted by Melraidin

Haven't got time to test the code, but possibly the input buffer still has the invalid input inside? Try flushing the buffer (I believe it's cin.clear(), but not positive) before each input.

thanks but cin.clear() is used before the BadInput prompt but it just seems to skip past it and go the the StopCharacter prompt still.

MrSmiley · 06-28-05

Quote:

Originally Posted by kris_cs1

Well, I may as well ask so that I understand it.
Why is it that it doesn't stop anyway when running these lines:

Code:

 
  cout << endl << "Press a key and \"Enter\": ";
  cin >> StopCharacter;

Ignore previous made point... dude, endl clears the current outstream buffer. To do something like that you would have to do

Code:

 cout << endl;
 cout << "Press any key\n";
 cin >> StopChar;

Melraidin · 06-28-05

Quote:

Originally Posted by kris_cs1

thanks but cin.clear() is used before the BadInput prompt but it just seems to skip past it and go the the StopCharacter prompt still.

I'll have to try loading this up in VS tomorrow, but have you actually tried adding the cin.clear () statements before each input?

kris_cs1 · 06-28-05

Quote:

Originally Posted by MrSmiley

Ignore previous made point... dude, endl clears the current outstream buffer. To do something like that you would have to do

Code:

cout << endl;
cout << "Press any key\n";
cin >> StopChar;

Oh, well thats what it says in the book... i just thought it moved onto the next line....

Quote:

Originally Posted by Melraidin

I'll have to try loading this up in VS tomorrow, but have you actually tried adding the cin.clear () statements before each input?

Yep... didn't seem to make a difference sorry

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