Warning: the material in this lab is quite challenging. It is highly recommended that you work with a partner.

The starter code for this lab is linked here Starter Code for Recurisve Reporters Lab

• 
  The autograder will fail if the block is not recurisve.
• 
  The autograder will fail if the block is not recurisve.

Command blocks using recursion have a structure like this:

There can be any number of recursive calls interspersed with other commands in the script.

You can also use reporters and recursion together! Reporters are slightly trickier, because a reporter can only report one value. So you can't do this:

(In fact, Snap! won't let you stack report blocks; since report ends the script, there is no connection tab below the block and you can't put anything directly below it. Optional exercise for hotshots: How did we make that picture?)

Instead, most of the time a recursive reporter call will be inside a combiner that attaches the result of the recursive call to some other value:

The combiner can be an arithmetic operator such as + or ×:

or a text string operator such as join or join words:

or a list operator such as append or in front of:

Note: Occasionally, the recursive call does appear directly inside the report:

(Wikipedia article on pig latin. Our block only accounts for the first rule.)

But most of the time, you won't go wrong if you start by thinking about what combining block to use.

☞ Don't go on until you understand what those four example scripts do, and how they do it.