Something of type Pipe (k,v) (k,v) m r would have to miss the last group of
values, no? Or maybe I'm not following. If upstream is following a
quasi-conduit strategy where await yields a Maybe and Nothing signals eof,
you could write, say:
pipeFoldValues :: (Monad m, Eq k) => (v -> v -> v) -> Pipe (Maybe
(k,v)) (k, v) m ()
pipeFoldValues append = go Nothing where
go (Just (k,v)) = do
a <- await
case a of
Nothing -> yield (k,v)
Just (k',v') | k == k' -> go (Just (k,append v v'))
Just (k',v') -> do
yield (k,v)
go (Just (k',v'))
go Nothing = do
a <- await
go a
or maybe a pipe that maintains this rule is better:
pipeFoldValues :: (Monad m, Eq k) => (v -> v -> v) -> Pipe (Maybe
(k,v)) (Maybe (k, v)) m r
pipeFoldValues append = go Nothing where
go (Just (k,v)) = do
a <- await
case a of
Nothing -> yield (Just (k,v)) >> forever (yield Nothing)
Just (k',v') | k == k' -> go (Just (k,append v v'))
Just (k',v') -> do
yield (Just (k,v))
go (Just (k',v'))
go Nothing = do
a <- await
go a
--
You received this message because you are subscribed to the Google Groups
"Haskell Pipes" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to haskell-pipes+unsubscr...@googlegroups.com.
To post to this group, send email to haskell-pipes@googlegroups.com.
