Easiest way to flip a boolean value?

Question

I just want to flip a boolean based on what it already is. If it\'s true - make it false. If it\'s false - make it true.

Here is my code excerpt:

swi         


        

Answer 1

You can flip a value like so:

myVal = !myVal;

so your code would shorten down to:

switch(wParam) {
    case VK_F11:
    flipVal = !flipVal;
    break;

    case VK_F12:
    otherVal = !otherVal;
    break;

    default:
    break;
}

Answer 2

flipVal ^= 1;

same goes for

otherVal

Answer 3

This seems to be a free-for-all ... Heh. Here's another varation, which I guess is more in the category "clever" than something I'd recommend for production code:

flipVal ^= (wParam == VK_F11);
otherVal ^= (wParam == VK_F12);

I guess it's advantages are:

• Very terse
• Does not require branching

And a just as obvious disadvantage is

• Very terse

This is close to @korona's solution using ?: but taken one (small) step further.

Answer 4

Clearly you need a flexible solution that can support types masquerading as boolean. The following allows for that:

template<typename T>    bool Flip(const T& t);

You can then specialize this for different types that might pretend to be boolean. For example:

template<>  bool Flip<bool>(const bool& b)  { return !b; }
template<>  bool Flip<int>(const int& i)    { return !(i == 0); }

An example of using this construct:

if(Flip(false))  { printf("flipped false\n"); }
if(!Flip(true))  { printf("flipped true\n"); }

if(Flip(0))  { printf("flipped 0\n"); }
if(!Flip(1)) { printf("flipped 1\n"); }

No, I'm not serious.

Answer 5

Clearly you need a factory pattern!

KeyFactory keyFactory = new KeyFactory();
KeyObj keyObj = keyFactory.getKeyObj(wParam);
keyObj.doStuff();


class VK_F11 extends KeyObj {
   boolean val;
   public void doStuff() {
      val = !val;
   }
}

class VK_F12 extends KeyObj {
   boolean val;
   public void doStuff() {
      val = !val;
   }
}

class KeyFactory {
   public KeyObj getKeyObj(int param) {
      switch(param) {
         case VK_F11:
            return new VK_F11();
         case VK_F12:
            return new VK_F12();
      }
      throw new KeyNotFoundException("Key " + param + " was not found!");
   }
}

:D

</sarcasm>

Answer 6

I prefer John T's solution, but if you want to go all code-golfy, your statement logically reduces to this:

//if key is down, toggle the boolean, else leave it alone.
flipVal = ((wParam==VK_F11) && !flipVal) || (!(wParam==VK_F11) && flipVal);
if(wParam==VK_F11) Break;

//if key is down, toggle the boolean, else leave it alone.
otherVal = ((wParam==VK_F12) && !otherVal) || (!(wParam==VK_F12) && otherVal);
if(wParam==VK_F12) Break;