[C++] LF help.

[P1raten]

I need a little help. When i type 10 it just says 1 when it should say 10.

//Main

#include <cstdlib>
#include <iostream>

using namespace std;
 
int main()
{
    char choice;
    for (;;){
     do {
    cout<<"\nChoose a number between 1-20.\n";
	cout<<"\n";
    cin>>choice;
	 } while ( choice < '1' || choice > '10' );
    switch (choice) {
           case '1':
				cout<<"\n";
				cout<<"1";
				cout<<"\n";
                break;
           case '2':
				cout<<"\n";
				cout<<"2";
				cout<<"\n";
                break;
           case '3':
				cout<<"\n";
				cout<<"3";
				cout<<"\n";
                break;
           case '4':
				cout<<"\n";
				cout<<"4";
				cout<<"\n";
                break;
		   case '5':
				cout<<"\n";
				cout<<"5";
				cout<<"\n";
                break;
		   case '6':
				cout<<"\n";
				cout<<"6";
				cout<<"\n";
                break;
		   case '7':
				cout<<"\n";
				cout<<"7";
				cout<<"\n";
                break;
		   case '8':
				cout<<"\n";
				cout<<"8";
				cout<<"\n";
                break;
		   case '9':
				cout<<"\n";
				cout<<"9";
				cout<<"\n";
                break;
		   case '10':
				cout<<"\n";
				cout<<"10";
				cout<<"\n";
                break;
           default:
                    cout<<"That is not an option";
                    
                }
 
}
	cout<<"\n";
return 0;


}

int stuff() {
	return 0;
}

FlameShield ON

[Cromon]

You read a char from the inputqueue. If you enter 10 to the queue the first character is 1 and the second 0. Therefore if you request one character from the queue you get 1. The better solution would be to request a whole line using std::cin.getline(params) and then try to convert it to an integer using sscanf (better than atoi cause it allows you to check if the text could not be converted while atoi only returns 0 on failure).

[piller]

atoi - C++ Reference

[P1raten]

You read a char from the inputqueue. If you enter 10 to the queue the first character is 1 and the second 0. Therefore if you request one character from the queue you get 1. The better solution would be to request a whole line using std::cin.getline(params) and then try to convert it to an integer using sscanf (better than atoi cause it allows you to check if the text could not be converted while atoi only returns 0 on failure).

atoi - C++ Reference

Just so you know; im a total n00b at C++.

[piller]

I´m not i c++ either. i´m delphian (shame on me)

would try something like this

//Main

#include <cstdlib>
#include <iostream>
#include <stdio.h>

using namespace std;
 
int main()
{
    char choice;
    char str [2];
    int i;

////////////////////////////////////////////

    sscanf (choice,"%d",str,&i); <-- here you get your input to integer i guess

and you can now go along with you code:

while ( choice < '1' || choice > '10' );
    switch (choice) {
           case '1':
				cout<<"\n";
				cout<<"1";
				cout<<"\n";
                break;
           case '2':
                        ...

but maybe im totally WRONG sir

[Cromon]

Ok, lets imagine you only allow 2-digit inputs then we use the following:

#include <iostream>

int main()
{
	char szInput[3] = { 0 };
	int iConverted = 0;

	std::cin.getline(szInput, 3);

	if(sscanf(szInput, "%i", &iConverted) != 1)
	{
		std::cout << "You did not enter a number!" << std::endl;
		return 0;
	}

	switch(iConverted)
	{
	case 0:
		std::cout << "0" << std::endl;
		break;
	case 1:
		std::cout << "1" << std::endl;
		break;
	}

	return 0;
}

[BonutDot]

Alternatively, define "choice" as some sort of numerical value, an int perhaps.

EDIT: Yeah cromon is right. Char is a bad idea all around for what you're doing.

[Cromon]

Thats not really good. Still choice is a char which means _1_ character gets read by cin. So this will still be the 1 and _not_ 10 because 10 are 2 digits!

Also the switch cannot work because '10' is 0x3130 and because the maximum of char is 0xFF it will in no case be 0x3130.

[Cypher]

And this thread is a testament to why mixing C and C++ is a bad idea.

The STL string class is there for a reason. Use it.
The STL stringsteam class is there for a reason. Use it.

Take input as a string, and use a stringstream to convert it to the target type.

If you're feeling lazy or you already have a Boost dependency, then Boost.LexicalCast is a quick and easy way to do the above without having to write the boiler-plate code.

This is assuming of course that you want to do the conversion, otherwise why not just take input directly as the target type?

[hexonflux]

What? Yea mixing C and C++ is only really called for when you learn
C first and move into C++. It just becomes habit. As far as using
stringstream and adding a lot of extra crap into the application, just
do it the simple way. Trying to over complicate things leads to major
mistakes and heavy runtime.

I've taken your code and made it into what I favored to be
what you were trying to do. I hope it helps.

#include <iostream>

using std::cout;
using std::cin;


int main()
{
    short choice = 0;

    while( choice >= 1 || choice <= 10 )
    {
        cout << "\nChoose a number between 1-10: ";
        cin >> choice;
        cout << "\n";

        switch( choice )
        {
            case 1:
                cout << 1;
                break;

            case 2:
                cout << 2;
                break;

            case 3:
                cout << 3;
                break;

            case 4:
                cout << 4;
                break;

            case 5:
                cout << 5;
                break;

            case 6:
                cout << 6;
                break;

            case 7:
                cout << 7;
                break;

            case 8:
                cout << 8;
                break;

            case 9:
                cout << 9;
                break;

            case 10:
                cout << 10;
                break;

            default:
                cout << "That is not an option.";
        }
        cout << "\n";
    }

    return 0;
}

- Hex

[Cromon]

And this thread is a testament to why mixing C and C++ is a bad idea.

Not at all! It is not "a bad idea" its just risky and you can very simple shoot yourself but on the other hand it can reduce not needed overhead!

[Cypher]

Not at all! It is not "a bad idea" its just risky and you can very simple shoot yourself but on the other hand it can reduce not needed overhead!

No. For the purposes C++ is used for in this context, in 99.99% of cases it is a BAD IDEA.

Very few programs are CPU bound and hence there is usually very little 'overhead' to 'reduce'. Yes, it's always good to avoid premature pessimization. But premature optimization is worse.

It's a lot easier to make a correct program fast than it is to make a fast program correct.