Definitely not as popular, but Arrow-ized effect systems are an interesting area that I've seen people exploring more lately. Jake Keuhlen spoke about it at La

Definitely not as popular, but Arrow-ized effect systems are an interesting area that I've seen people exploring more lately. Jake Keuhlen spoke about it at LambdaConf this year [0] [1], and John De Goes spoke a bit on the notion of Arrow-ized IO in the `zio` library for Scala that offers an alternative interface for `IO` effects [2]. Will Fancher has also written a bit on the concept of "Free Arrows", but it's a much deeper dive (IMO) than the previous resources [3]. [0] Keuhlen's Repo: https://github.com/jkeuhlen/talks/tree/master/extensibly-free-arrows https://github.com/jkeuhlen/talks/tree/master/extensibly-fre... [1] Keulen's Slides: https://github.com/jkeuhlen/talks/blob/master/Extensibly%20Free%20Arrows.pdf https://github.com/jkeuhlen/talks/blob/master/Extensibly%20F... [2] https://github.com/scalaz/scalaz-zio/blob/master/core/shared/src/main/scala/scalaz/zio/KleisliIO.scala https://github.com/scalaz/scalaz-zio/blob/master/core/shared... [3] https://elvishjerricco.github.io/2017/03/10/profunctors-arrows-and-static-analysis.html https://elvishjerricco.github.io/2017/03/10/profunctors-arro...