相关疑难解决方法(0)

I made two pattern views for a list-like class.

infixr 5 :<
pattern (:<) :: Stream s => Token s -> s -> s
pattern b :< bs <- (uncons -> Just (b, bs))
  where b :< bs = cons b bs

pattern Nil :: Stream s => s
pattern Nil <- (uncons -> Nothing)
  where Nil = empty

uncons signature: uncons :: (Stream s) => s -> Maybe (Token s, s).

Suppose I also have function that uses …