Cross-platform pure functional logging library for Scala. Integrates with well known JVM logging frameworks and can also be used standalone in ScalaJS or Scala Native.
Go towards the project's website for more information.
You gotta give credit where credit is due.
scala-colog is a Scala fork of Dimitrii Kovanikov's
colog, the Haskell library that initially explored the idea of composable loggers. For more information about the internals read this very descriptive blog post by its Author.