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Elementary cellular automaton/Random number generator: Difference between revisions
Elementary cellular automaton/Random number generator (view source)
Revision as of 11:22, 17 October 2016
, 7 years ago→{{header|Haskell}}: Added general random data generation
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<lang Haskell>import CellularAutomata (runCA, rule, fromList)
import Data.List (unfoldr)
import Control.Comonad
rnd = fromBits <$> unfoldr (pure . splitAt 8) bits
where size = 80
bits = extract <$> runCA (rule 30) (fromList (1:replicate size 0))
{{Out}}
<pre>λ> take 10 rnd
[220,197,147,174,117,97,149,171,240,241]</pre>
Using the rule 30 CA it is possible to determine the <code>RandomGen</code> instance which could be utilized by the <code>Random</code> class:
<lang Haskell>import System.Random
instance RandomGen (Cycle Int) where
next c = let x = c =>> step (rule 30) in (fromBits (view x), x)
split c = (c, fromList (reverse (view c)))</lang>
<pre>λ> let r30 = fromList [1,0,1,0,1,0,1,0,1,0,1,0,1] :: Cycle Int
λ> take 15 $ randoms r30
[7509,4949,2517,2229,2365,2067,6753,5662,5609,7576,2885,3017,2912,5081,2356]
λ> take 30 . randomRs ('A','J') $ r30
"DHJHHFJHBDDFCBHACHDEHDHFBAEJFE"</pre>
We can compare it with standard generator on a small integer range, using simple bin counter:
<pre>λ> let bins lst = [ (n, length (filter (==n) lst)) | n <- nub lst]
λ> bins . take 10000 . randomRs ('A','J') $ r30
[('D',1098),('H',1097),('J',1093),('F',850),('B',848),('C',1014),('A',1012),('E',1011),('G',1253),('I',724)]
λ> bins . take 10000 . randomRs ('A','J') <$> getStdGen
[('G',975),('B',1035),('F',970),('J',1034),('I',956),('H',984),('C',1009),('E',1023),('A',1009),('D',1005)]</pre>
=={{header|J}}==
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