-- | -- Module: Math.NumberTheory.Canon.SpecialFunctions -- Copyright: (c) 2018-2019 Frederick Schneider -- Licence: MIT -- Maintainer: Frederick Schneider -- Stability: Provisional -- -- This module defines numerous functions associated with massive numbers. -- This is an excellent resource: http://googology.wikia.com/wiki/Googology_Wiki module Math.NumberTheory.Canon.SpecialFunctions ( moserFunc, moserTriangle, moserSquare, moserPentagon, mega, megiston, moser, knuth, conwayChain, conwayGuy, genGrahamFunc, grahamFunc, grahamsNumber, ackermann, ackermann3 -- , sudan ) where import Math.NumberTheory.Canon moserFunc :: Canon -> Canon -> Canon -> Canon moserTriangle, moserSquare :: Canon -> Canon moserPentagon, mega, megiston, moser :: Canon -- | Generalized Moser function: https://en.wikipedia.org/wiki/Steinhaus%E2%80%93Moser_notation -- to do: non-recursive definition? moserFunc nP mP pP | cIntegral nP && cIntegral mP && cIntegral pP && nP >= c1 && pP >= c3 = m' nP mP pP | otherwise = error "The parameters to the Moser function must all be integral with n >= 1 and p >= 3." where m' n m p | n < 1 = error "n must be >= 1 in the Moser function" | m > c1 = m' (m' n c1 p) (m-c1) p | p > c3 = m' n n (p-c1) | otherwise = n <^ n -- | Moser Triangle (see Wikipedia link) moserTriangle n = moserFunc n c1 c3 -- | Moser Square (see Wikipedia link) moserSquare n = moserFunc n c1 c4 -- | Moser Pentagon (see Wikipedia link) moserPentagon = mega -- | Mega: "2 in a circle" (see Wikipedia link) mega = moserFunc c2 c1 c5 -- | Megiston: "10 in a circle" (see Wikipedia link) megiston = moserFunc c10 c1 c5 where c10 = makeCanon 10 -- | Moser number; "2 in a mega-gon" (see Wikipedia link) moser = moserFunc c2 c1 mega -- "2 in a mega-gon" ackermann :: Canon -> Canon -> Canon ackermann3 :: Canon -> Canon -> Canon -> Canon -- | Ackermann function (https://en.wikipedia.org/wiki/Ackermann_function) ackermann m n | cIntegral m && cIntegral n && m >= c0 && n >= c0 = a m n | otherwise = error "m and n must both be integral in the Ackermann function with m >= 0 and n >= 0" where a m' n' | m' == c0 = n' + c1 | m' < c3 && n' == c0 = a (m' - c1) c1 | m' < c3 = a (m' - c1) $ a m' (n - c1) | otherwise = -3 + conwayChain [2, n+3, m-2] -- | The original 3 parameter Ackermann function ackermann3 mP nP pP | cIntegral mP && cIntegral nP && cIntegral pP && nP >= c0 && pP >= c0 = a3 mP nP pP | otherwise = error "m, n and p must all be integral in the Ackermann3 function" where a3 m n p | n < c0 || p < c0 = error "ackermann3 Both n and p must be >= 0" | p == c0 = m + n | p == c1 = m * n | p == c2 = m <^ n | p == c3 = m <^> (n + c1) | n == c0 = m | p == c4 && n == 2 = m <^> (1 + m <^> (m + c1)) -- Found while testing. Helps along calculation | p == c4 && n > 2 = m <^> (1 + a3 m (n - c1) p) | otherwise = a3 m (a3 m (n - c1) p) (p - c1) {- Status ackermann3 2 2 4 = 2 <^> 17 -- could also be written as 2 <^> (1 + 2<^>3) so this is between 2 <<^>> 3 and 2 <<^>> 4 ackermann3 2 3 4 = 2 <^> {1 + 2 <^> 17} ackermann3 2 4 4 ... Generated error saying special cases in cHyperOp not covered when more than two items. XXX ackermann3 3 2 4 = 3 <^> (1 + 3 <^> (2*2)) ackermann3 3 3 4 ... Hung initially but workaround added ackermann3 7 3 4 = 7 <^> {1 + 7 <^> {1 + 7 <^> (2^3)}} ackermann3 5 4 4 = 5 <^> {1 + 5 <^> {1 + 5 <^> {1 + 5 <^> (2 * 3)}}} -- note the folding based on the second term ackermann3 2 2 5 ... Hangs Here's why (stepping through the logic) a3 2 2 5 = a3 2 (a3 2 1 5) 4 where a3 2 1 5 = a3 2 (a3 2 0 5) 4 = a3 2 2 4 a3 2 2 5 = a3 2 (a3 2 2 4) 4 = a3 2 (2<^>17) 4. So, this folding step would have to be done an incredible number of times. ToDo: Is there an elegant closed form expression? x n 4 is between x <<^>> n+ 1 and x <<^>> n + 2. -} {- ToDo: Fix and add later -- | The Sudan function created by Gabriel Sudan, a student of David Hilbert (https://en.wikipedia.org/wiki/Sudan_function) sudan :: Canon -> Canon -> Canon -> Canon sudan n x y | not (cIntegral n) || not (cIntegral x) || not (cIntegral y) || n < 0 || x < 0 || y < 0 = error "All input to the sudan function must be integral and >= 0" | otherwise = s n x y where s n x y | n == 0 = x + y | n > 0 && y == 0 = x | n == 1 = s c1 c0 y + x * 2 <^ y | otherwise = s (n-1) snxym1 (snxym1 + y) where snxym1 = s n x (y-1) -} genGrahamFunc :: Canon -> Integer -> Canon grahamFunc :: Integer -> Canon grahamsNumber :: Canon -- | Calls the generalized Graham function with value 3 grahamFunc = genGrahamFunc c3 -- | Graham's Number (https://en.wikipedia.org/wiki/Graham%27s_number) grahamsNumber = grahamFunc 64 -- | Generalized Graham Function genGrahamFunc cP nP | cIntegral cP && cP >= c1 && nP >= 1 = gGF cP nP | otherwise = error "c and n must be Integral and both c and n >= 1 in the generalized Graham function" where gGF c n | n > 1 = cApplyHy (gGF c (n -1)) [c,c] True -- recursively defined | otherwise = c <<<^>>> c -- Hexation or 4 arrows knuth :: Canon -> Canon -> Canon -> Canon -- | Knuth's Up Arrow Notation, analagous to hyperoperations (https://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation) knuth a n b = cApplyHy (c2 + n) [a,b] True conwayChain :: [Canon] -> Canon -- | Conway Chained-Arrow Notation (https://en.wikipedia.org/wiki/Conway_chained_arrow_notation) -- This function will try to reduce generalized conway chain notation down to humble hyperoperations (or better) conwayChain l' | all (\c -> cIntegral c && c > c0) l' = cc l' | otherwise = error "ConwayChain: Each element in the input list/chain must be integral and > 0" where cc ch | null ch = error "Logic Error: conwayChain requires a non-zero list." | head ch == c1 = c1 | otherwise = f (takeWhile (/= c1) ch) f c = case l of 0 -> c1 -- in this context we have stripped out the 1s so we can assume 1 1 -> p 2 -> p <^ q 3 -> knuth p r q -- "simple" hyperoperation -- Beyond length 3, we may never come back. Note: We string out the 1s _ | p == c2 && q == c2 -> c4 -- Property #6 | otherwise -> cc $ x ++ [cc (x ++ [s-1, v])] ++ [v-1] -- Rule #4 where l = length c (p, q, r) = (head c, c !! 1, c!! 2) x = take (l-2) c -- x is like the prefix chain from the wiki formula (s, v) = (c !! (l-2), last c) -- second to last AND "very" last terms -- Note: conwayChain [x,2,2,2] = x x. (e.g. conwayChain [3,2,2,2] = 3 ~^~ 3, which is the hyperoperator for level 10) {- Some low-level level 4 examples v = map (\l -> (l, conwayChain $ map makeCanon l)) [[3,2,2,2], [3,2,3,2], [3,3,2,2], [3,3,3,2], [3,2,2,3], [3,3,2,3]] mapM_ (putStrLn . show) v ([3,2,2,2], 3 ~^~ 3) -- Level 10 = 3^2 + 1 Hyper Operation. Note: The library converts: x 2 TO x x ([3,2,3,2], 3 3) -- which is 3 3 ([3,3,2,2],3 ~~|<<<<^>>>>|~~ 3) -- Level 29 = 3^3 + 2 Hyper Operation ([3,3,3,2],3 >>>|~~ 3}> 3) -- which is 3 3 ([3,2,2,3],3 3}> 3}> 3}> 3}> 3}> 3}> 3) ([3,3,2,3],3 >>>|~~ 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3}> 3) Note: conwayChain [3,3,3,3] = conwayChain [3,3, [3,3,2,3], 2] so you have to iteratively embed the hyper operations a massive number of times Note: For perspective, Graham's number has been shown to be between [3,3,64,2] and [3,3,65,2]! -} conwayGuy :: Canon -> Canon -- | Conway-Guy function is a conwayChain of n copies of n. conwayGuy n = conwayChain (replicate (fromIntegral n) n) -- Kind of unrelated but interesting: goodstein rep: https://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation#Numeration_systems_based_on_the_hyperoperation_sequence