Problem Statement

The   Look and say sequence   is a recursively defined sequence of numbers studied most notably by   John Conway.

The   look-and-say sequence   is also known as the   Morris Number Sequence,   after cryptographer Robert Morris,   and the puzzle   What is the next number in the sequence 1,   11,   21,   1211,   111221?   is sometimes referred to as the Cuckoo's Egg,   from a description of Morris in Clifford Stoll's book   The Cuckoo's Egg.

Sequence Definition

An example:

Write a program to generate successive members of the look-and-say sequence.

Let's start with the solution:

function lookAndSay S
   put 0 into C
   put char 1 of S into lastChar
   repeat with i = 2 to length(S)
      add 1 to C
      if char i of S is lastChar then next repeat
      put C & lastChar after R
      put 0 into C
      put char i of S into lastChar
   end repeat
   return R & C + 1 & lastChar
end lookAndSay

on demoLookAndSay
   put 1 into x
   repeat 10
      put x & cr after message
      put lookAndSay(x) into x
   end repeat
   put x after message
end demoLookAndSay