While loops with no content

Is using a blank while loop frowned upon? Here's the bit I have in my code:

for slot=1, 16 do
  print("Place a block in slot"..slot..".")
    while turtle.getItemCount(slot) == 0 do
	  --Waiting for block to be placed in [slot]
    end
end

I don't think there should be a problem with this, but it occurred to me that this may be some sort of "bad practice" or something.

The program will eventually error with "too long without yielding" if there hasn't been put an item into the slot; put a sleep in there and you're good to go.
If you want to go even fancier, use

os.pullEvent("turtle_inventory")

so it would only check when the inventory has actually changed.

In this particular case, you can, but only because turtle.getItemCount( slot ) yields internally. If it did not, your code would be terminated after 10 seconds.

KingofGamesYami, on 24 July 2014 - 10:07 PM said:

In this particular case, you can, but only because turtle.getItemCount( slot ) yields internally. If it did not, your code would be terminated after 10 seconds.

False, turtle.getItemCount() doesn't yield, so the code would error

wieselkatze, on 24 July 2014 - 10:06 PM said:

If you want to go even fancier, use

os.pullEvent("turtle_inventory")

so it would only check when the inventory has actually changed.

How exactly would I implement this? I'm confused on what context to use it in.

Just put that in your while loop:

while turtle.getItemCount( slot ) == 0 do
  os.pullEvent("turtle_inventory")
end

That would yield at that point and wait until ComputerCraft triggers the specific event.

@wieselkatze: All the turtle functions yield internally, to my knowledge.

@ReconTurtle: Pretty much like this…

for slot=1, 16 do
  print("Place a block in slot"..slot..".")
    while turtle.getItemCount(slot) == 0 do
      os.pullEvent( "turtle_inventory" ) --#wait for an item to enter/leave inventory
          --Waiting for block to be placed in [slot]
    end
end

Edit: Ninja'd

Thanks to both you guys for your help, I appreciate it :D/>
Edit: Where can I find a list of these events, for future reference?

KingofGamesYami, on 24 July 2014 - 10:27 PM said:

@wieselkatze: All the turtle functions yield internally, to my knowledge.
- snip -

Apparently not. Try that loop without any yield inside it.

@ReconTurtle:
Look at the wiki page, there is everything you will need ;)/>

Alternatively, you can always use sleep(0). Less elegant, but effective nonetheless.

turtle.getItemCount(), turtle.getItemSpace() and turtle.getFuelLevel() do not pull events. 1.6 might've changed that, but probably not. I would assume turtle.getSelectedSlot() and turtle.getFuelLimit() (both added by 1.6) also don't pull events. These information-gathering functions should be the only exceptions.

I've also noticed the "all turtle commands pull events" dis-information around the place, and must admit I've failed to correct it lately.

Forget about using sleep. It has a much higher overhead than just waiting for a turtle inventory event. It'll work, yeah, but that's no excuse to use it. :P/>

Edit: Well, I suppose it's only fair to point out that the turtle_inventory event was only added to ComputerCraft recently-ish; if you're on a build prior to CC 1.55, then your options boil down to using a sleep/timer solution, or asking the user to press a key when ready and waiting for the key event.