Documentation

An effect which allows a regular Monad m into the Sem ecosystem. Monadic actions in m can be lifted into Sem via sendM.

For example, you can use this effect to lift IO actions directly into Sem:

sendM (putStrLn "hello") :: Member (Lift IO) r => Sem r ()

That being said, you lose out on a significant amount of the benefits of Sem by using sendM directly in application code; doing so will tie your application code directly to the underlying monad, and prevent you from interpreting it differently. For best results, only use Lift in your effect interpreters.

Consider using trace and runTraceIO as a substitute for using putStrLn directly.