monad-log

This package provide a mtl style MonadLog class and a concrete monad transformer LogT, the main difference between this package and monad-logger are: Base monad has to be an instance of MonadIO. Parametrized logging environment for extensibility. Basic logging environment type(Label,Loc,NameSpace,ThreadId) are included, and you can easily make your own. JSON logging built-in. default to fast-logger backend, with good stdout and file support. If you are an application author, you can use LogT transformer, it's just a specialized reader monad to inject `Logger env`. If you are a library author, you should do following two things: make your monad stack an instance of MonadLog, usually you can do this by embedding `Logger env` into your monad's reader part. provide a default formatter, and API to run with customized formatter.