16 строки
689 B
TeX
16 строки
689 B
TeX
All those 3 functions look almost the same. Since haskell is about abstraction, we would never really write any of those like that. Instead, we will write a function that generalizes all 3.
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\vspace{\baselineskip}
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\\
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\pause
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I'll give you the type signature, can you guess how the implementation looks like?
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\begin{haskellcode}
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map :: (a -> b) -> [a] -> [b]
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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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map :: (a -> b) -> [a] -> [b]
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map f [] = []
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map f (x:xs) = f x : map f xs
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\end{haskellcode}
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So we don't really know what the function \code{f} does, but we know that it converts one element of the list to something else. We \emph{map} a function over a list! Hence the name. |