Changing bool values to opposite of the initial value

Question

This maybe sound strange to you but I'm too lazy to write everytime like

if (threadAlive)
{
            threadAlive = false;
}
        else
{
            threadAlive = true;
}

isn't there is something like int++ or int-- to change bool value to opposite of its value?

Solution 1

Just do this:

threadAlive = !threadAlive;

Solution 2

Yes, there is!

threadAlive ^= true;

(this is a C# joke, in the most general case it won't work in C/C++/Javascript (it could work in C/C++/Javascript depending on some conditions), but it's true! ^ is the xor operator)

Solution 3

This would do it:

threadAlive = !threadAlive;

The correct term is Toggle

Solution 4

The logical negation operator ! is a unary operator that negates its operand. It is defined for bool and returns true if and only if its operand is false and false if and only if its operand is true:

threadAlive = !threadAlive;

Solution 5

Use the ! operator:

bool b = true;

b = !b;   // b is now false

View more solutions

Comments

[p.s.w.g]

@user1046403 in C / C++ you could possibly write a custom operator that makes it simpler, in C# this is as good as it gets.

[Joel]

Even if you can write a custom operator, do everyone a favor and don't do that. b = !b is idiomatic to anyone who understands the language.

[user1046403]

maybe if there would be something like threadAlive!! that would be awesome. How could I write a custom operator? any help?

[p.s.w.g]

I didn't expect that to work in C#, but it does. +1 for ingenuity.

[R. Martinho Fernandes]

Your problem has been solved. Don't try to make it into a worse one. (Also, please pick up some learning material for one of C or C++ or C# or whichever you are learning)

[sehe]

It's a bad joke, because the type of threadAlive wasn't specified. This would lead "not true" to be "true" for the majority of values for int, e.g.

[xanatos]

@sehe There is a C# tag. But added a note about languages.

[James Kanze]

@p.s.w.g In C, there are no custom operators. In C++, at least one parameter of a custom operator must be a user defined type, or a reference to a user defined type, which bool is not. (In either language, of course, you could write a macro which does it. A technique which commonly goes under the name of obfuscation.)

[p.s.w.g]

@user1046403 Writing a custom operator is a different question entirely. 1) pick a language, 2) do some research, 3) try something out 4) if you have trouble, ask that as a new question on SO.

[James Kanze]

It should work in C++ as well, provided threadAlive has type bool (and since he uses it as a condition in an if, that should be a safe assumption---although the language does allow other types, with implicit conversion, and I've even seen some programmers use them).

[p.s.w.g]

@JamesKanze I haven't used C++ since college, so I wasn't sure. I didn't want to say it was flatly impossible.

[sehe]

@xanatos Ah, I see, C# makes it illegal to use ^= true unless threadAlive is of type System.Boolean. That means you redefined the question (assuming threadAlive is bool) as well as reduced the scope to 1/3 (only answering for C#)

[tuseau]

@sehe The original question is marked with a boolean tag so I think it's a fair assumption. Don't think he redefined the question at all, also this is the most elegant solution.