any way to transform this into a `tailrec`? And ge...

# announcements

[elect]

any way to transform this into a tailrec? And get rid of the !!?

while (window.flags has Wf.ChildWindow && window.parentWindow != null)
    window = window.parentWindow!!

[Shawn]

as far as tailrec goes, something like this probably

tailrec fun findWindow(window: Window): Window {
  return if (window.flags has Wf.ChildWindow && window.parentWindow != null) {
    findWindow(window.parentWindow)
  } else {
    window
  }
}

[elect]

window.parentWindow is Window?, that's the problem

[Shawn]

also if I had to guess the problem you’re seeing with smart casting is probably because window.parentWindow is a var or a val with a computed getter

[elect]

var indeed

[Shawn]

you’re probably just going to have to cache in a local val

[elect]

uh, yeah

[Shawn]

or, well, bleh, it’s probably actually the combined if

[elect]

this appears to trigger no warning from the compiler

tailrec fun findWindow(window: Window): Window {
                val parent = window.parentWindow
                return if (window.flags has Wf.ChildWindow && parent != null) findWindow(parent) else window
            }

[elect]

but findWindow isnt the last call.. or is it?

[Shawn]

compiler doesn’t complain

[elect]

no

[Shawn]

tailrec doesn’t mean that the recursive call has to literally be the last visible line in a function

[Shawn]

there just can’t be logic after the function call. (and the other branch needs to be terminal)

[Shawn]

you could invert that if to make it look more tail recursive, but it’s really the same thing

[Shawn]

tailrec fun findWindow(window: Window): Window {
  val parentWindow = window.parentWindow
  return if (Wf.ChildWindow !in window.flags || parentWindow == null) {
    window
  } else {
    findWindow(parentWindow)
  }
}

[elect]

got it, thanks