Repeat Until () (block)

Repeat Until ()
repeat until <>
Category	Control
Type	Stack
Introduced in	1.1

The Repeat Until () block is a Control block and a C block. Blocks held inside this block will loop until the specified boolean statement is true, in which case the code beneath the block (if any) will execute. This loop is in similar nature to a while loop in some other programming languages.

Example Uses

As this block loops pieces of code until a condition is true, the block is the best way to run code until a desired condition has been reached. Some common uses include:

• Moving a sprite until its X or Y position is at a certain amount

repeat until <(x position) = [100]>
move (10) steps

• Having a sprite stick to the mouse until the mouse is not down

repeat until <not <mouse down?>>
go to (mouse pointer v)

• Waiting for an event while performing an action

repeat until <. . .::grey>
. . .

• Repeating a script for a specific amount of time

reset timer
repeat until <(timer) > (limit)>
  . . .
end

• Repeating a question until the user answers correctly

repeat until <(answer) = (correct answer)>
ask [question] and wait
end

Delays

After each iteration of the loop, a delay of 1/30 of a second (or one frame) is added before the next iteration continues. This allows for animations to be run smoother. However, if you don't want this delay, turn on turbo mode, or put it inside of a custom block set to run without screen refresh. However, you must be certain that it will stop at some point, as otherwise, there can be significant issues with performance.

Warning:

Putting a loop that never ends inside of a custom block set to run without screen refresh will cause the project to lag tremendously.

Workaround

Main article: List of Block Workarounds

This block can be worked around with the following code:

define repeat until
forever
if <. . .::grey> then
stop [this script v]
end
. . .

You can also make sure the script inside runs at least once, similar to do while loops in some programming languages:

define at least once: repeat until
forever
. . .
if <. . .::grey> then
stop [this script v]
end

This should be avoided when making one sprite one script projects, however.

See Also

• Repeat ()
• Forever
• Forever If ()