Редактирование: Binary flags (раздел)

=== Checking bitflags ===

Okay, so now we learned how to add a flag, now to check for one. This time AND (&) will come in handy.

Above we did...

  var/f = 255 //0b11111111
  var/e = 0   //0b11111111
  v3 = c & f  // since 1 and anything = anything, v3 didn't change from c.
  v4 = c & e  // since anything and 0 = 0, v4 was set to 0.

We can use a combination of both to help us. If we want to check for the leg disability, we can do it like this:

  mob/proc/check_disability(var/dis)
    if( disabilities & dis )
      return 1
    else
      return 0

The proc above takes a parameter and checks whether the bit is set. Let's suppose we have the same situation as we left off at above, with disabilities set to 0b0110. 

If we call check_disability(DISABILITY_EAR) the proc will check:

disabilities & dis

0b0110 & 0b0010 = 0b0010

So the value is positive, which means the if check will pass and the proc will return 1 (truth), otherwise it will return 0 (false). The value of disabilities in this proc is not changed.

If we however check for the eye disability by calling check_disability(DISABILITY_EYE)

0b0110 & 0b0001 = 0b0000

The calculation yields a 0, so the if fails, and the proc returns a 0 (false)