317: Mainline

Now for the recursion trick: you replace powerOfTwo in recursivePowerOfTwo by recursivePowerOfTwo itself.

Integer method definition • instance 
recursivePowerOfTwo 
  self = 0 
    ifTrue: [^ 1] 
    ifFalse: [^ 2 * (self - 1) recursivePowerOfTwo] 
Workspace
Transcript show: 4 recursivePowerOfTwo printString; cr  
Transcript 
16