[Haskell-cafe] repeat confusion
borgauf at gmail.com
Fri Apr 23 16:31:46 UTC 2021
I'm in Bird's *Thinking Functionally with Haskell *and he has this code to
transpose a matrix based on a list of row lists
transpose :: [[a]] -> [[a]]
transpose [xs] = [[x] | x <- xs]
transpose (xs:xss) = zipWith (:) xs (transpose xss)
then he says transpose can be rewritten with this pattern
transpose  = ...
what could be the rest of it? The answer he gives is
transpose2 :: [[a]] -> [[a]]
transpose2  = repeat 
transpose2 (xs:xss) = zipWith (:) xs (transpose2 xss)
where repeat  gives an infinite list of repetitions. And, he says, note
transpose [xs] = zipWith (;) xs (repeat ) = [[x] | x <- xs]
I suppose I get this last equation, but I don't understand repeat in
transpose2. Can someone explain this to me?
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