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{-# OPTIONS_GHC -O -ddump-rules #-}
-- #2486
--
-- The thing to look for here is that specialisations for fib and tak
-- at both Int and Double are indeed generated; hence -ddump-rules
module Main where
import System.Environment
import Numeric
main = do
n <- getArgs >>= readIO . head
let m = n-1
a = 27 + fromIntegral n
putStr $
line "Ack" [3,n] (ack 3 n) show ++
line "Fib" [a] (fib a :: Double) (\n -> showFFloat (Just 1) n []) ++
line "Tak" [3*m,2*m,m] (tak (3*m) (2*m) m :: Int) show ++
line "Fib" [3] (fib 3 :: Int) show ++
line "Tak" [3,2,1] (tak 3 2 1 :: Double) show
where
line pre a r f = pre ++ "(" ++ csv f a "" ++ "): " ++ f r ++ "\n"
csv f [a] s = s ++ f a
csv f (a:b) s = s ++ f a ++ "," ++ csv f b s
ack :: Int -> Int -> Int
ack 0 n = n+1
ack m 0 = ack (m-1) 1
ack m n = ack (m-1) (ack m (n-1))
fib :: (Num a, Ord a) => a -> a
fib n = if n >= 2 then fib (n-1) + fib (n-2) else 1
tak :: (Num a, Ord a) => a -> a -> a -> a
tak x y z = if y < x then tak (tak (x-1) y z) (tak (y-1) z x) (tak (z-1) x y) else z
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