Ben Rudiak-Gould writes:
start :: IO ctx feed :: ctx -> Buffer -> IO () commit :: ctx -> IO a
'feed' cannot have this signature because it needs to update the context.
Sure it can -- it's just like writeIORef :: IORef a -> a -> IO ().
I guess it's mood to argue that point. I don't want a stream processor to have a global state, so using an internally encapsulated IORef is not an option for me. I am looking for an more _general_ API, not one that forces implementation details on the stream processor. That's what my StreamProc data type does already. :-)
start :: ctx feed :: ctx -> Buffer -> IO ctx commit :: ctx -> a
In this interface contexts are supposed to be immutable Haskell values, so there's no meaning in creating new ones or finalizing old ones.
I don't want to restrict the API to immutable contexts. A context could be anything, _including_ an IORef or an MVar. But the API shouldn't enforce that.
I would implement feedSTUArray and friends as wrappers around the Ptr interface, not as primitive computations of the stream processor.
I think it's impossible to do this safely, but it would be great if I were wrong.
wrap :: (Storable a, MArray arr a IO) => Ptr a -> Int -> IO (arr Int a) wrap ptr n = peekArray n ptr >>= newListArray (0,n) Peter