On Sat, Jan 24, 2015 at 07:46:52PM +0100, Gautier DI FOLCO wrote:
data ImapF next = Select DirectoryName (Maybe DirectoryDescription -> next) | Noop (DirectoryDescription -> next) | Search MailSearch (Maybe [UID] -> next) -- Functor instance type Imap = Free ImapF
searchAll :: Imap (Maybe [UID]) searchAll = liftF $ Search undefined id select :: DirectoryName -> Imap (Maybe DirectoryDescription) select directory = liftF $ Select directory id
My main problem is the following: if I do a select of an unknown directory, I should stop the computation.
What do you mean you "should stop the computation"? Do you mean the interpretation of the free monad should be forced to stop? If so, doesn't making the type of the `Select` constructor Select DirectoryName (DirectoryDescription -> next) achieve this? That way if the interpreter talks issues a select command to the server and fails to receive a `DirectoryDescription` in return then it is forced to stop. Tom