Question regarding implicit parameters... The GHC manual says: "Dynamic binding constraints behave just like other type class constraints in that they are automatically propagated." But the following code produces an error: --------------------------------------------------------------------------------------------------------- main = do var <- newIORef (0::Int) let ?global_counter = var in f f = do a <- get_unique putStr (showInt a "\n") b <- get_unique putStr (showInt b "\n") c <- get_unique putStr (showInt c "\n") get_unique :: (?global_counter :: IORef Int) => IO Int get_unique = readIORef ?global_counter ---------------------------------------------------------------------------------------------------------- If "(?global_counter :: IORef Int)" were a class constraint the type signature for 'f' could be derived automatically... but we get: Unbound implicit parameter (?global_counter::IORef a) arising from use of `get_unique' at Test.hs:17:13-22 Is this a bug? Is there some reason why this is not possible? (and if it is not possible shouldn't the documentation be changed to reflect this)... Keean.