RosettaCodeData/Task/Fibonacci-sequence/Purity/fibonacci-sequence-3.purity

import Histo

data Fib3 = Histo . Memoize
            <
              const One,
              (p1 =>
              <
                const One,
                (p2 => Add (outl $p1) (outl $p2)). UnmakeCofree
              > (outr $p1)) . UnmakeCofree
            >