@@ -27,6 +27,52 @@
2727--
2828-- @
2929--
30+-- Another common case that you have some sort of App monad that's
31+-- based on ReaderT with some Config state. This is a perfect place to
32+-- insert read-only katip state:
33+--
34+-- @
35+--
36+-- import Katip as K
37+--
38+-- data Config = Config {
39+-- logNamespace :: K.Namespace
40+-- , logContext :: K.LogContexts
41+-- , logEnv :: K.LogEnv
42+-- -- whatever other read-only config you need
43+-- }
44+--
45+-- newtype App m a = App {
46+-- unApp :: ReaderT Config m a
47+-- } deriving (Functor, Applicative, Monad) -- more instances as needed
48+--
49+--
50+-- -- These instances get even easier with lenses!
51+-- instance (MonadIO m) => K.Katip (App m) where
52+-- getLogEnv = asks logEnv
53+-- -- with lens:
54+-- -- getLogEnv = view logEnv
55+-- localLogEnv f (App m) = App (local (\s -> s { logEnv = f (logEnv s)}) m)
56+-- -- with lens:
57+-- -- localLogEnv f (App m) = App (local (over logEnv f) m)
58+--
59+--
60+-- instance (MonadIO m) => K.KatipContext (App m) where
61+-- getKatipContext = asks logContext
62+-- -- with lens:
63+-- -- getKatipContext = view logContext
64+-- localKatipContext f (App m) = App (local (\s -> s { logContext = f (logContext s)}) m)
65+-- -- with lens:
66+-- -- localKatipContext f (App m) = App (local (over logContext f) m)
67+-- getKatipNamespace = asks logNamespace
68+-- -- with lens:
69+-- -- getKatipNamespace = view logNamespace
70+-- localKatipNamespace f (App m) = App (local (\s -> s { logNamespace = f (logNamespace s)}) m)
71+-- -- with lens:
72+-- -- localKatipNamespace f (App m) = App (local (over logNamespace f) m)
73+--
74+-- @
75+--
3076-- To get up and running, the workflow is generally:
3177--
3278-- * Set up a 'LogEnv' using 'initLogEnv'.