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Hofstadter Figure-Figure sequences: Difference between revisions
Hofstadter Figure-Figure sequences (view source)
Revision as of 10:18, 24 October 2011
, 12 years agoAdded Haskell version
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Line 56:
(princ "Ok")</lang>output<lang>First of R: (1 3 7 12 18 26 35 45 56 69)
Ok</lang>
=={{header|Haskell}}==
<lang haskell>import Data.List (delete, sort)
-- Functions by Reinhard Zumkeller
ffr n = rl !! (n - 1) where
rl = 1 : fig 1 [2 ..]
fig n (x : xs) = n' : fig n' (delete n' xs) where n' = n + x
ffs n = rl !! n where
rl = 2 : figDiff 1 [2 ..]
figDiff n (x : xs) = x : figDiff n' (delete n' xs) where n' = n + x
main = do
print $ map ffr [1 .. 10]
let i1000 = sort (map ffr [1 .. 40] ++ map ffs [1 .. 960])
print (i1000 == [1 .. 1000])</lang>
Output:
<pre>[1,3,7,12,18,26,35,45,56,69]
True</pre>
=={{header|J}}==
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