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-- Type declaration : -- [a] - a linked list of any type -- x -> y - function that accepts x and returns y mylen :: [a] -> Integer -- Declare the length of the empty list to be 0 mylen [] = 0 -- x:xs == the list whose first item (the head) is x and the rest (the tail) -- is xs. mylen (x:xs) = 1 + (mylen xs) |

fib :: Integer -> Integer fib 0 = 0 fib 1 = 1 fib a = (fib (a-1)) + (fib (a-2)) |

-- (a,b) is a tuple whose first element is a and its second is b fibo_helper :: Integer -> (Integer,Integer) fibo_helper 0 = (0,1) -- Notice the use of the closure (where) to assign two temporary values fibo_helper n = (b,a+b) where (a,b) = fibo_helper (n-1) -- (fst (a,b)) = a fibo n = (fst (fibo_helper n)) |

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Written by Shlomi Fish