PROPOSAL: Some more 'Applicative' combinators

[Iavor Diatchki]

Hello,
I propose that we add the following combinators to the
'Control.Applicative' module:

skipMany   :: (Alternative f) => f a -> f ()
skipMany p  = skipSome p <|> pure ()

skipSome   :: (Alternative f) => f a -> f ()
skipSome p  = p *> skipMany p

endBy      :: (Alternative f) => f a -> f b -> f [a]
endBy p s   = many (p <* s)

endBy1     :: (Alternative f) => f a -> f b -> f [a]
endBy1 p s  = some (p <* s)

sepBy      :: (Alternative f) => f a -> f v -> f [a]
sepBy p s   = sepBy1 p s <|> pure []

sepBy1     :: (Alternative f) => f a -> f v -> f [a]
sepBy1 p s  = (:) <$> p <*> many (s *> p)


Any objections?  Deadline for discussion is 2 weeks from now, which
would be the 20th of Jan.

-Iavor