????if Else????

[cjohnson412]

Ok so i have to create a program that has a basic menu (i.e. apple - a, orange -o, juice - j ) I need to create a loop that allows the customer to enter (a, o, j ) in as an option, yet at the same time rejects any other syllable thats not in the menu by letting the user know they made an invalid entry. Should I use an If else statement for this, if not can what can I use, would some one be able to show me an example and link to show more of this... Thanks for you help in advance.
cj

[cyberfish]

if you are sure the user is going to enter a single character input, you can use a "switch" statement with the default case being invalid entry.

[bradszy]

#include <iostream>
using namespace std;
int main()
{
int MENUANSWER;
MAINMENU:
cout<<"[1] For Apple"<<endl;
cout<<"[2] For Orange"<<endl;
cout<<"[3] For Juice"<<endl;
cin>>MENUANSWER;

if (MENUANSWER==1)
{
          //Apple chosen
}

else if (MENUANSWER==2)
{
        //Orange chosen
}

else if (MENUANSWER==3)
{
       //Juice chosen
}

else
{
       //Invalid choice
      goto MAINMENU;
}

return 0;
}

[Elysia]

switch(x)
{
	case 'a': /* Do something; */ break;
	default: // User did not enter something acceptable
}

And don't use goto; use a loop instead.

[bradszy]

May I ask why not?

[Raigne]

Simply put it is unsafe. There ARE many explanations of this on the board, and on google. 5 minutes of searching will get you hours of proof.

EDIT:
Also is this really that hard?

int main()
{
	bool quit = false;
	char input;
	while (!quit)
	{
		std::cin >> input;
		std::ignore();
		switch(input)
		{
		case 'q':
			quit = true;
			break;
		default:
			break;
		}
	}
}

I swear people are afraid of a few extra lines of code, for better readability and code security.

[vart]

better write your loops in the following manner:

while (std::cin >> input)
{
	std::ignore();
	switch(input)
	{
	case 'q':
		break;
	default:
		break;
	}
}

[Elysia]

May I ask why not?

Mostly because it causes spaghetti code. In other words, it creates hard to read and maintainable code because goto can jump just about anywhere in the code.

[cyberfish]

There are cases where gotos can actually make the code more readable and maintainable (for example, breaking out of nested loops). However, in most other cases, it is bad.

[Elysia]

Indeed, but that is pretty much all that it's good for in C++. Almost.

[iMalc]

There are cases where gotos can actually make the code more readable and maintainable (for example, breaking out of nested loops).

Such a comment is not helpful here. No beginner should ever use a goto; It's counter-productive to their necessary learning of structured programming.

Don'y use all CAPITALS for variable names. It's ugly and harder to read, and clashes with most people's coding conventions whereby only constants and macros are all uppercase.

[robatino]

Such a comment is not helpful here. No beginner should ever use a goto; It's counter-productive to their necessary learning of structured programming.

But the statement was true, and it's not inconceivable that a beginner might write code that requires breaking out of a nested loop. Specific unnecessary uses of goto should be pointed out, and after finding out that 99% of them are in fact unnecessary, they'll get the idea. But I don't think they should be told that it should never be used.