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punksta/fibonacci by accumulators

Created September 17, 2016 21:49
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fibonacci recursion with accumulators
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fibonacci by accumulators
fibonacci :: Integer -> Integer
fibonacci 0 = 0
fibonacci n | n > 0 = fibInner n 1 1
| n < 0 = fibInner n 1 1
fibInner :: Integer -> Integer -> Integer -> Integer
fibInner (-1) r r2 = r
fibInner 1 r r2 = r
fibInner n r r2 | n > 0 = helper (n - 1) r2 (r + r2)
| n < 0 = - helper (n + 1) r2 (r + r2)
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