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This question already has an answer here:
What are some and many in Control.Applicative.Alternative good for? If I write something like some $ Just 42, it seems to cause infinite recursion, which seems not very useful...
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They make sense, when used as a parser combinator.
somemeans, that the parser is applied as often as possible, but at least once.manyis similar, but allows no parse. In case ofMaybe,Just ...never "fails", thus your parser loops.