Monad Logger Sample

sample_monadLogger.hs

-- {-# LANGUAGE OverloadedStrings #-}

import Data.Text
import Control.Monad.Trans
import Control.Monad.Trans.Maybe
import Control.Monad.Trans.State
import Control.Monad.Trans.Identity
import Control.Monad.Identity
import Control.Monad.Logger

--
-- MaybeT
--

-- >let w0 = do return 1:: MaybeT IO Int
-- >runMaybeT w0
-- Just 1
-- >let w0 = do return 2:: MaybeT IO Int
-- >runMaybeT w0
-- Just 2
-- >let w1 = do liftIO $ print "aaa"; return 2:: MaybeT IO Int
-- >runMaybeT w1
-- "aaa"
-- Just 2

--
-- Log + MaybeT
--

logMaybe00 :: LoggingT (MaybeT IO) Int
logMaybe00 =  do 
    monadLoggerLog (Loc{loc_filename="monad_log_sample.hs", loc_module="foo", loc_package="bar", loc_start=(0,0), loc_end=(0,0)}) (pack "log source") LevelDebug  (toLogStr $ pack "a")
    liftIO $ putStrLn "logMaybe00"
    return 2
-- >runMaybeT $ runStdoutLoggingT logMaybe00
-- [Debug#log source] a @(bar:foo monad_log_sample.hs:0:0)
-- logMaybe00
-- Just 2

logMaybe00' :: NoLoggingT (MaybeT IO) Int -- Change type from LoggingT to NoLoggingT, keeping the same implementaion. 
logMaybe00' =  do 
    monadLoggerLog (Loc{loc_filename="monad_log_sample.hs", loc_module="foo", loc_package="bar", loc_start=(0,0), loc_end=(0,0)}) (pack "log source") LevelDebug  (toLogStr $ pack "a")
    liftIO $ putStrLn "logMaybe00"
    return 2
-- >runMaybeT $ runNoLoggingT logMaybe00'
-- logMaybe00
-- Just 2
-- >
-- 

logMaybe01 :: LoggingT (MaybeT IO) Int
logMaybe01 =  do 
    msg <- liftIO $ getLine
    mylog msg
    liftIO $ putStrLn "aaa"
    return 2

mylog :: MonadLogger m => String -> m ()
mylog msg =  monadLoggerLog (Loc{loc_filename="", loc_module="", loc_package="", loc_start=(0,0), loc_end=(0,0)}) (pack "") LevelDebug  (toLogStr $ pack msg)

-- >runMaybeT $ runStdoutLoggingT logMaybe01
-- zxzzxzxzx
-- [Debug] zxzzxzxzx @(: :0:0)
-- aaa
-- Just 2
-- >

--
-- StateT
--
state00 :: StateT [Int] IO Int
state00 = do
    x:xs<-get 
    put xs
    modify ((:) 9)
    liftIO $ print x
    return $ sum xs

-- >runStateT state00 [1,2,3]
-- 1
-- (5,[9,2,3])
-- >
-- 

--
-- Log + StateT
--
logState00 :: LoggingT (StateT [Int] IO) Int
logState00 =  do
    x:xs <- lift get
    lift $ put xs
    mylog $ "***" ++ (show xs) ++ "***"
    x:xs <- lift get
    lift $ put xs
    mylog $ "***" ++ (show xs) ++ "***"
    return 5

-- >runStateT (runStdoutLoggingT logState00) [1,2,3]
-- [Debug] ***[2,3]*** @(: :0:0)
-- [Debug] ***[3]*** @(: :0:0)
-- (5,[3])
-- >