Hello Cale,
Saturday, January 14, 2006, 12:22:08 AM, you wrote:
CG> On 13/01/06, John Goerzen wrote:
i want to answer, but Gale covered all that i have to say :) the only
additions is that i use more old-fashioned Hugs-compatible declarations
instead of GADT-style
CG> data Connection where
CG> Conn :: (IsConnection c) => c -> Connection
data Connection = forall c . (IsConnection c) => Conn c
and that i use the "delegation" pattern:
class (Show h) => Stream h where
vClose :: h -> IO ()
......
vSetEncoding :: h -> Encoding -> IO ()
vGetEncoding :: h -> IO Encoding
data WithEncoding h = WithEncoding h (IORef Encoding)
openWithEncoding encoding h = do
e <- newIORef encoding
return (WithEncoding h e)
instance (Stream h) => Stream (WithEncoding h) where
vClose (WithEncoding h _) = vClose h
vIsEOF (WithEncoding h _) = vIsEOF h
vMkIOError (WithEncoding h _) = vMkIOError h
vReady (WithEncoding h _) = vReady h
......
vSetEncoding (WithEncoding h e) = writeIORef e
vGetEncoding (WithEncoding h e) = readIORef e
you can see WithEncoding type as a one adding server-specific features
to general driver implementation. of course, this idea of "stream
transformers" is more general that you really requested, but the
"delegation" pattern will remain the same
--
Best regards,
Bulat mailto:bulatz@HotPOP.com
