gistfile1.io

fakeClosure := Object clone do(
  memo := Map clone
  fibmemo := block(num, #note 'blocks' are lexically scoped
    memo atPut(0 asString, 0)
    memo atPut(1 asString, 1)
    fibhelp := method(num,
      one := memo at((num-1) asString)
      two := memo at((num-2) asString)
      if(one == nil
        , one = fibhelp(num-1,memo)
          memo atPut((num-1) asString, one)
        )
      if(two == nil
        , two = fibhelp(num-2,memo)
          memo atPut((num-2) asString, two)
        )
      one + two
    )
    fibhelp(num,memo)
  ) setIsActivatable(true)
)

fibmemo := fakeClosure getSlot("fibmemo")
fibmemo(12) println