Haskell: some and many [duplicate]
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27-10-2019 - |
문제
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...
해결책
They make sense, when used as a parser combinator. some
means, that the parser is applied as often as possible, but at least once. many
is similar, but allows no parse. In case of Maybe
, Just ...
never "fails", thus your parser loops.
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