let cache = newref({})

proc fib(n)
  if (n < 1) then
    return 1
  else
    let c = readref(cache)
    if haskey(c, tostring(n)) then
      return c[tostring(n)]
    else
      let r = (fib((n - 1)) + fib((n - 2)))
      modifyref(cache, fn (c) addkey(c, tostring(n), r) endfn)
     return r
    endif
  endif
endproc

println(fib(135))