Problem Statement

Given a string containing uppercase characters (A-Z), compress repeated 'runs' of the same character by storing the length of that run, and provide a function to reverse the compression. The output can be anything, as long as you can recreate the input with it.

Note: the encoding step in the above example is the same as a step of the Look-and-say sequence.

Let's start with the solution:

#import std
#import nat

encode = (rlc ==); *= ^lhPrNCT\~&h %nP+ length

decode = (rlc ~&l-=digits); *=zyNCXS ^|DlS/~& iota+ %np

test_data = 'WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW'

#show+

example = 

<
   encode test_data,
   decode encode test_data>