module NFib where

instruction primadd "addint" :: Int! -> Int! -> Int!
instruction primsub "subint" :: Int! -> Int! -> Int!

main  = nfib 27

-- strict nfib
nfib n  = case n of
            0  -> 1
            1  -> 1
            n  -> case (case (case primsub n 2 of
                                     n2 -> nfib n2
                             ) of
                         x2 -> case (case primsub n 1 of
                                            n1 -> nfib n1
                                    ) of
                                 x1 -> primadd x1 x2
                       ) of
                    x -> primadd 1 x