while loop and failbit with other conditions unexpected behavior

[bryan177mcsc]

Why doesn't this work?

while (!(std::cin >> stat) || (stat != "hp" || stat != "str" || stat != "aff"))
{
	std::cin.clear();
	std::cin.ignore();
	std::cout << "Invalid Entry.\n";
}

But this does?

while (!(std::cin >> stat) || stat!= "hp")
{
	std::cin.clear();
	std::cin.ignore();
	std::cout << "Invalid Entry.\n";
}

I am trying to stop a failbit but at the same time stop the user from entering none related strings. The only string I wish to allow are "hp", "str" or "aff". Why does it work with one string but not other options?

I realize I could do this with an if statement but I'd rather use while loops.

[Peter87]

If stat != "hp" is false then you can be sure stat != "str" will be true because it can't be equal to "hp" and "str" at the same time. Since you use || it's enough that one of them is true for the whole expression to be true, and that is always the case here. I think you should probably use && instead of || when testing the different string values because you want the loop to run once more if ALL of them is true, not just if ONE of them is true.

[bryan177mcsc]

Wow.
This post is probably a reminder that I should not be doing this at 3AM.
Time to go to bed, good explanation Peter thanks a lot for your help.