Understanding exclamation equals

Projects Programming
1

in the following line, I see an equals sign, then a space and then an exclamation point. What does that mean? I found that the reverse version without the space (!=) means "not equal to"

ledAstate = ! ledAstate;

2

It's the logical NOT operation.

3

AWOL:
It's the logical NOT operation.

I gotcha. I at least understand the logic side of it. If used in an "if" statement, what is it actually doing? What is the outcome of using it?

For example...

if (currentMillis - prevLedAMillis >= ledAInterval) {
   prevLedAMillis += ledAInterval;
   ledAstate = ! ledAstate;
4

You're not using it in an if statement, you're using it in a conditional code block.

It inverts its operand, ledAstate, and assigns the result to ledAstate.

5

Consider the following:

   boolean cold, hot;

   cold = true;

   // Later in the program...
   hot = !cold;

If we start out with an environment where the room is cold, so the cold sensor is true. Therefore, "not cold" (i.e., ! cold) can be interpreted as hot. You will often see the NOT operator used to toggle a variable, perhaps between OFF and ON:

   sensor = ! sensor;  // Reverses its state from ON to OFF, or from OFF to ON.
7

Does it make a difference if there is a space between the ! and the variable? Compiling issues?

sensor = ! sensor

vs

sensor = !sensor

9

Vampyrewolf:
Does it make a difference if there is a space between the ! and the variable? Compiling issues?

sensor = ! sensor

vs

sensor = !sensor

You can always write a small sketch to show what happens :wink: