RosettaCodeData/Task/Fibonacci-sequence/Haskell/fibonacci-sequence-17.hs

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Haskell
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2018-06-22 20:57:24 +00:00
f (n,(a,b)) = (2*n,(a*a+b*b,2*a*b+b*b)) -- iterate f (1,(0,1)) ; b is nth