Programming Forums > Application Development > C++

jayme · Nov 25th, 2005, 12:55 AM

i added your code to that, but it didnt work.. was hoping someone could show me how i would change the segment i posted above to work with what you posted.

Cache · Nov 25th, 2005, 1:22 AM

I'm just a newb so don't mind me if I'm wrong, but shouldn't the above look more like:

(Toggle Plain Text)

int i;
	
	while (1)
	{
	  cout<<"number?\n"<<endl;
	  cin>>i;
	  if (i<0 || i >18)
	  {
			  break;
	  }	  
	}

Cache · Nov 25th, 2005, 1:22 AM

Quote:

Originally Posted by Cache

I'm just a newb so don't mind me if I'm wrong, but shouldn't the above look more like:

(Toggle Plain Text)

int i;
	
	while (1)
	{
	  cout<<"number?\n"<<endl;
	  cin>>i;
	  if (i<0 || i >18)
	  {
			  break;
	  }	  
	}

EDIT: Yup I'm wrong..sorry about that..

And now I've just quoted myself trying to edit my original post too..lol.:o

Cache · Nov 25th, 2005, 1:51 AM

OK, in a bid to make up for my last two ridiculous posts I've come up with the folowing:

(Toggle Plain Text)

#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
	
	char input[10];
	int i;
	
	while(1)
	{
		 cout<<"number?\n"<<endl;
		 cin.getline(input,10);
		 i = atoi(input);
		 if ((i<=0) || (i>=20))
		 {
			cout << "\nERROR: Invalid selection\n";
			cout << "Press any key to retry. . .\n\n";
			cin.get();
			continue;
		 } else
		   {
			   break;
		   }
	}   
	
	cout<<"\nyou entered "<<i<<"\n"<<endl;
	
	system("pause");
	
	return 0;
}

Note you will have to include 'cstdlib' for atoi() to work.

bl00dninja · Nov 25th, 2005, 2:26 AM

i thought my solution was stupid. i'm sure there's a better way to check for type compatibility.

cache's most recent solution seems to work the best.

Cache · Nov 25th, 2005, 2:47 AM

One problem I have noticed though, atoi() seems to convert all non integer values (a, b, c, ect) to 0. So you wouldn't be able to use anything that =0.

DaWei · Nov 25th, 2005, 8:10 AM

There is a lot of voodoo and bullshit being recommended in this thread, which is a Bad Thang. The perils of input have been addressed on the forum, but let's cover them again, rather than recommend a nasty search.

Incidentally, Andro is on the right track, with the right ideas. Kilo, you should not recommend using non-portable code when such isn't necessary.

You rarely can control what the user provides. You only have the chance to validate it and clean it up. As an aid in that process, most input functions provide return values. One checks these to see if the user has managed to break the input mechanism. It's easy to do. If you're asking for input and not checking status you are either new (the most common case) or a fool (not uncommon enough). Cin is a collection of methods. The extraction operator (>>) doesn't return status directly (it returns the stream), so one must use additional methods. Among these are .good (), .bad () and .fail ().

Some input functions, among them cin, offer to do more for you than merely gather keystrokes. They offer conversion. They know how to convert, every bit as well as atoi knows how to convert, and most likely, better. Some things aren't convertible; in a conversion situation they will either break something or produce garbage. One must check for these things.

The example procedure illustrates some of this. If one is really picky, one distinguishes between bad (severe), fail, eof, and such.

(Toggle Plain Text)

#include <iostream>

using namespace std;

int getStrength ()
{
    unsigned int strength;
    unsigned int tries = 0;

    cout << endl << "Enter strength: ";
    while (true)
    {
        if (tries > 3)
        {
            cout << "You just can't get it, can you?" << endl;
            return -1;
        }
        // The following clears the error bits for the stream,
        // in case some usage broke it.
        cin.clear ();
        // Adjust the stream related pointers.  For istreams,
        // this effectively clears content.  It's possible for
        // it to fail.  Some istreams might not have buffers;
        if (cin.sync () == -1) return -1;
        cin >> strength;
        if (!cin.good ()) cout << "Invalid input; try again: ";
        else if (strength > 20) cout << "Invalid number, try again: ";
        else return strength;
        tries++;
    }
    return -1;
}

-=PARADOX=- · Nov 25th, 2005, 8:14 AM

What the hell...

Just do this:

(Toggle Plain Text)

int main()
{

        int x;
        while ( cin >> x )
                cout << x << endl;
        cout << "You not entered a number..."<< endl;

        system("PAUSE");
        return 0;
}

DaWei · Nov 25th, 2005, 8:43 AM

Because that doesn't get the job done....

-=PARADOX=- · Nov 25th, 2005, 8:44 AM

Why is that?

Nov 25th, 2005, 1:22 AM	#12
Cache Hobbyist Join Date: Sep 2005 Posts: 261 Rep Power: 4	I'm just a newb so don't mind me if I'm wrong, but shouldn't the above look more like: (Toggle Plain Text) int i; while (1) { cout<<"number?\n"<<endl; cin>>i; if (i<0 \|\| i >18) { break; } } int i; while (1) { cout<<"number?\n"<<endl; cin>>i; if (i<0 \|\| i >18) { break; } }

Nov 25th, 2005, 1:51 AM	#14
Cache Hobbyist Join Date: Sep 2005 Posts: 261 Rep Power: 4	OK, in a bid to make up for my last two ridiculous posts I've come up with the folowing: (Toggle Plain Text) #include <iostream> #include <cstdlib> using namespace std; int main() { char input[10]; int i; while(1) { cout<<"number?\n"<<endl; cin.getline(input,10); i = atoi(input); if ((i<=0) \|\| (i>=20)) { cout << "\nERROR: Invalid selection\n"; cout << "Press any key to retry. . .\n\n"; cin.get(); continue; } else { break; } } cout<<"\nyou entered "<<i<<"\n"<<endl; system("pause"); return 0; } #include <iostream> #include <cstdlib> using namespace std; int main() { char input[10]; int i; while(1) { cout<<"number?\n"<<endl; cin.getline(input,10); i = atoi(input); if ((i<=0) \|\| (i>=20)) { cout << "\nERROR: Invalid selection\n"; cout << "Press any key to retry. . .\n\n"; cin.get(); continue; } else { break; } } cout<<"\nyou entered "<<i<<"\n"<<endl; system("pause"); return 0; } Note you will have to include 'cstdlib' for atoi() to work.

Nov 25th, 2005, 2:26 AM	#15
bl00dninja Programming Guru Join Date: Oct 2004 Location: namespace std Posts: 1,246 Rep Power: 5	i thought my solution was stupid. i'm sure there's a better way to check for type compatibility. cache's most recent solution seems to work the best. __________________ i put on my robe and wizard hat... Have you ever heard of Plato, Aristotle, Socrates?...Morons.

Nov 25th, 2005, 8:10 AM	#17
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	There is a lot of voodoo and bullshit being recommended in this thread, which is a Bad Thang. The perils of input have been addressed on the forum, but let's cover them again, rather than recommend a nasty search. Incidentally, Andro is on the right track, with the right ideas. Kilo, you should not recommend using non-portable code when such isn't necessary. You rarely can control what the user provides. You only have the chance to validate it and clean it up. As an aid in that process, most input functions provide return values. One checks these to see if the user has managed to break the input mechanism. It's easy to do. If you're asking for input and not checking status you are either new (the most common case) or a fool (not uncommon enough). Cin is a collection of methods. The extraction operator (>>) doesn't return status directly (it returns the stream), so one must use additional methods. Among these are .good (), .bad () and .fail (). Some input functions, among them cin, offer to do more for you than merely gather keystrokes. They offer conversion. They know how to convert, every bit as well as atoi knows how to convert, and most likely, better. Some things aren't convertible; in a conversion situation they will either break something or produce garbage. One must check for these things. The example procedure illustrates some of this. If one is really picky, one distinguishes between bad (severe), fail, eof, and such. (Toggle Plain Text) #include <iostream> using namespace std; int getStrength () { unsigned int strength; unsigned int tries = 0; cout << endl << "Enter strength: "; while (true) { if (tries > 3) { cout << "You just can't get it, can you?" << endl; return -1; } // The following clears the error bits for the stream, // in case some usage broke it. cin.clear (); // Adjust the stream related pointers. For istreams, // this effectively clears content. It's possible for // it to fail. Some istreams might not have buffers; if (cin.sync () == -1) return -1; cin >> strength; if (!cin.good ()) cout << "Invalid input; try again: "; else if (strength > 20) cout << "Invalid number, try again: "; else return strength; tries++; } return -1; } #include <iostream> using namespace std; int getStrength () { unsigned int strength; unsigned int tries = 0; cout << endl << "Enter strength: "; while (true) { if (tries > 3) { cout << "You just can't get it, can you?" << endl; return -1; } // The following clears the error bits for the stream, // in case some usage broke it. cin.clear (); // Adjust the stream related pointers. For istreams, // this effectively clears content. It's possible for // it to fail. Some istreams might not have buffers; if (cin.sync () == -1) return -1; cin >> strength; if (!cin.good ()) cout << "Invalid input; try again: "; else if (strength > 20) cout << "Invalid number, try again: "; else return strength; tries++; } return -1; } __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 25th, 2005, 8:14 AM	#18
-=PARADOX=- Programmer Join Date: Oct 2005 Location: Portugal Posts: 53 Rep Power: 3	What the hell... Just do this: (Toggle Plain Text) int main() { int x; while ( cin >> x ) cout << x << endl; cout << "You not entered a number..."<< endl; system("PAUSE"); return 0; } int main() { int x; while ( cin >> x ) cout << x << endl; cout << "You not entered a number..."<< endl; system("PAUSE"); return 0; }

Nov 25th, 2005, 2:47 AM	#16
Cache Hobbyist Join Date: Sep 2005 Posts: 261 Rep Power: 4	One problem I have noticed though, atoi() seems to convert all non integer values (a, b, c, ect) to 0. So you wouldn't be able to use anything that =0.

Nov 25th, 2005, 8:43 AM	#19
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Because that doesn't get the job done.... __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 25th, 2005, 8:44 AM	#20
-=PARADOX=- Programmer Join Date: Oct 2005 Location: Portugal Posts: 53 Rep Power: 3	Why is that?

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