Ackerman in Haskell (Jaco Malan)

main.hs

-- A program to calculate the values of Ackerman's function from (0, 0) to (5, 5).
--    Copyright (C) 2018  Jaco Malan

--    This program is free software: you can redistribute it and/or modify
--    it under the terms of the GNU General Public License as published by
--    the Free Software Foundation, either version 3 of the License, or
--    (at your option) any later version.

--    This program is distributed in the hope that it will be useful,
--    but WITHOUT ANY WARRANTY; without even the implied warranty of
--    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--    GNU General Public License for more details.

--    You should have received a copy of the GNU General Public License
--    along with this program.  If not, see <https://www.gnu.org/licenses/>.

ack :: (Integer, Integer) -> Integer
ack (m, n)
  | m == 0 = n + 1
  | n == 0 && m > 0 = ack (m - 1, 1)
  | m > 0 && n > 0 = ack (m - 1, ack (m, n - 1))

main :: IO ()
main = do
  let nums = concatMap (\m -> map (\n -> (m, n)) [0..5]) [0..5]
  let ans = map (\m -> "Ackerman " ++ show m ++ ": " ++ (show . ack) m) nums
  mapM_ putStrLn ans

Ackerman's function

Ackerman's function is a famous function in computer science which proves that some tasks cannot be de-recursed (broken down into loops).

Compiling

• You can easily compile this program using GHC (Glascow Haskell Compiler), just use $ ghc main.hs optionally use '-O' for optimizations since this is a heavily CPU-intensive program.

Licensing

This gist is licensed under the GNU GPL v3.0.

Author: Jaco Malan