Índices de números de Fibonacci

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1. Haskell

   import Data.List indiceFib :: Integer -> Maybe Integer indiceFib n | esTermino n = Just ((genericLength (terminos n)) - 1) | otherwise = Nothing esTermino :: Integer -> Bool esTermino n = last (terminos n) == n terminos :: Integer -> [Integer] terminos n = takeWhile (<= n) fibonaccis fibonaccis :: [Integer] fibonaccis = fs where (xs,ys,fs) = (zipWith (+) ys fs, 1:xs, 0:ys)

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   import Data.List     indiceFib :: Integer -> Maybe Integer indiceFib n | esTermino n  = Just ((genericLength (terminos n)) - 1)             | otherwise = Nothing   esTermino :: Integer -> Bool esTermino n = last (terminos n) == n   terminos :: Integer -> [Integer] terminos n = takeWhile (<= n) fibonaccis   fibonaccis :: [Integer] fibonaccis = fs where (xs,ys,fs) = (zipWith (+) ys fs, 1:xs, 0:ys)

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2. Haskell

   fibConIndices :: [(Integer,Integer)] fibConIndices = aux 0 1 0 where aux m n x = (m,x) : aux n (m+n) (x+1) indiceFib :: Integer -> Maybe Integer indiceFib x | elem x xs = Just $ head [n | (y,n) <- fibConIndices, y == x] | otherwise = Nothing where xs = takeWhile (<=x) (map fst fibConIndices)

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   fibConIndices :: [(Integer,Integer)] fibConIndices = aux 0 1 0      where aux m n x = (m,x) : aux n (m+n) (x+1)   indiceFib :: Integer -> Maybe Integer indiceFib x | elem x xs = Just $ head [n | (y,n) <- fibConIndices, y == x]             | otherwise = Nothing             where xs = takeWhile (<=x) (map fst fibConIndices)

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3. Haskell

   indiceFib :: Integer -> Maybe Integer indiceFib n | n == f = Just p | otherwise = Nothing where (p,f) = head $ dropWhile (\(_,f) -> f < n) numeraFibs numeraFibs :: [(Integer,Integer)] numeraFibs = (0,0): (1,1): zipWith (\(_,b) (c,d) -> (c+1,b+d)) numeraFibs (tail numeraFibs)

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   indiceFib :: Integer -> Maybe Integer indiceFib n | n == f    = Just p             | otherwise = Nothing   where (p,f) = head $ dropWhile (\(_,f) -> f < n) numeraFibs         numeraFibs :: [(Integer,Integer)]         numeraFibs = (0,0): (1,1): zipWith (\(_,b) (c,d) -> (c+1,b+d))                      numeraFibs (tail numeraFibs)

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4. Haskell

   import Data.List indiceFib :: Integer -> Maybe Integer indiceFib x | find (>=x) fibs /= Just x = Nothing | otherwise = Just (genericLength $ takeWhile (<x) fibs) fibs :: [Integer] fibs = aux 0 1 where aux x y = x : aux y (x+y)

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   import Data.List   indiceFib :: Integer -> Maybe Integer indiceFib x | find (>=x) fibs /= Just x = Nothing             | otherwise = Just (genericLength $ takeWhile (<x) fibs)   fibs :: [Integer] fibs = aux 0 1     where aux x y = x : aux y (x+y)

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5. Haskell

   import Data.List indiceFib :: Integer -> Maybe Integer indiceFib x | notElem x xs = Nothing | otherwise = Just (genericLength xs -1) where xs = takeWhile (<=x) fibs fibs :: [Integer] fibs = 0:1:[ x+y | (x,y) <- zip fibs (tail fibs)]

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   import Data.List   indiceFib :: Integer -> Maybe Integer indiceFib x | notElem x xs = Nothing             | otherwise = Just (genericLength xs -1)         where xs = takeWhile (<=x) fibs   fibs :: [Integer] fibs = 0:1:[ x+y | (x,y) <- zip fibs (tail fibs)]

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6. Haskell

   indiceFib (n) := block([a:0,b:1,c:1,p:0], unless n <= a do (a : b, b : c, c : a + b, p : p + 1), if n = a then print(n,"es el",p,"-ésimo número de Fibonacci.") else print(n,"no es un número de Fibonacci."))$

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   indiceFib (n) := block([a:0,b:1,c:1,p:0],   unless n <= a do    (a : b,     b : c,     c : a + b,     p : p + 1),   if n = a    then print(n,"es el",p,"-ésimo número de Fibonacci.")    else print(n,"no es un número de Fibonacci."))$

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7. Haskell

   import Data.List indiceFib :: Integer -> Maybe Integer indiceFib x | last xs == x = Just (genericLength xs - 1) | otherwise = Nothing where xs = takeWhile (<=x) fibs fibs :: [Integer] fibs = 0 : scanl (+) 1 fibs

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   import Data.List   indiceFib :: Integer -> Maybe Integer indiceFib x | last xs == x  = Just (genericLength xs - 1)             | otherwise     = Nothing     where xs = takeWhile (<=x) fibs   fibs :: [Integer] fibs = 0 : scanl (+) 1 fibs

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