I am having issues with type signatures for the resourceHandler action
below. I haven't figured out what I'm doing wrong to cause the wrong
type to be returned. It looks like Haskell is inferring that I'm
returning a function from this action, when from the type signature I've
specified, that is not what I'm wanting. The gist of the code is based
on the request_method of the passed in HttpRequest, choose an action to
run and pass it the needed parameters.
the error:
renao.hs:6:4:
Couldn't match `HttpResponse' against `IO HttpResponse'
Expected type: IO HttpResponse
Inferred type: IO (IO HttpResponse)
In the expression: return $ (handler session request)
In the result of a 'do' expression: return $ (handler session request)
the code:
import HttpMessage
import HttpSession
resourceHandler :: HttpSession -> HttpRequest -> IO HttpResponse
resourceHandler session request = do
return $ handler session request
where
handler = which_handler request
which_handler r = case request_method r of
Get -> get_resources
Head -> last_modified
Post -> update_resources
Put -> create_resources
Delete -> delete_resources
get_resources :: HttpSession -> HttpRequest -> IO HttpResponse
get_resources session request = undefined
-- ... the same stubbed definition for the other handlers
(last_modified, etc)
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