Feigenbaum constant calculation: Difference between revisions

=={{header|Haskell}}==

<lang haskell>import Data.List (mapAccumL, foldl') --' strict

feigenbaumApprox :: Int -> [Double]

feigenbaumApprox mx = snd $ mitch mx 10

where

mitch :: Int -> Int -> ((Double, Double, Double), [Double])

mitch mx mxj =

mapAccumL

(\(a1, a2, d1) i ->

let a =

foldl' --' strict variant of foldl

(\acc v ->

let (x, y) =

iterate

(\(p, q) ->

(acc - (p * p), 1.0 - ((2.0 * p) * q)))

(0.0, 0.0) !!

(2 ^ i)

in acc - (x / y))

(a1 + (a1 - a2) / d1)

[1 .. mxj]

d = (a1 - a2) / (a - a1)

in ((a, a1, d), d))

(1.0, 0.0, 3.2)

(take mx [2 ..])

main :: IO ()

main =

(putStrLn . unlines) $

zipWith

(\i s -> justifyRight 2 ' ' (show i) ++ '\t' : s)

[1 ..]

(show <$> feigenbaumApprox 13)

where

justifyRight n c s = drop (length s) (replicate n c ++ s)</lang>

{{Out}}

<pre> 1 3.2185114220380866

2 4.3856775985683365

3 4.600949276538056

4 4.6551304953919646

5 4.666111947822846

6 4.668548581451485

7 4.66906066077106

8 4.669171554514976

9 4.669195154039278

10 4.669200256503637

11 4.669200975097843

12 4.669205372040318

13 4.669207514010413</pre>