some-and-many - w3toppers.com

‘some’ and ‘many’ functions from the ‘Alternative’ type class [duplicate]

some and many can be defined as: some f = (:) <$> f <*> many f many f = some f <|> pure [] Perhaps it helps to see how some would be written with monadic do syntax: some f = do x <- f xs <- many f return (x:xs) So some f runs … Read more

What are Alternative’s “some” and “many” useful for?

TL;DR: some is one or more, many is 0 or more results collected from performing the same computation over and over by the familiar maximal munch rule. For this to make sense, some state passing (and alteration) must take place reducing the domain of possibilities somehow, otherwise it will repeat ad infinitum. And state passing … Read more