25 lines
551 B
TeX
25 lines
551 B
TeX
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There's one more important recursion pattern. Imagine you want the sum of all numbers of a list, so the function type signature would be:
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\begin{haskellcode}
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sum :: [Int] -> Int
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\end{haskellcode}
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Solution?
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\pause
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\begin{haskellcode}
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sum :: [Int] -> Int
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sum [] = 0
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sum (x:xs) = x + sum xs
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\end{haskellcode}
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\pause
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Or the product:
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\begin{haskellcode}
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prod :: [Int] -> Int
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prod [] = 1
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prod (x:xs) = x * prod xs
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\end{haskellcode}
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\pause
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Or the length:
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\begin{haskellcode}
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length :: [a] -> Int
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length [] = 0
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length (x:xs) = 1 + length xs
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\end{haskellcode}
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