Application design with a stack of monads 2019

Functional Programming is often seen as a nice tool for small-scale concerns, not as a tool for application design. However, functional programming comes with interesting tools aimed at solving these boring (or deemed boring) concerns: dependency inversion, observability). A functional solution, called a monad stack, allows to combine all this cross-cutting concerns and behaviours with no magic (or not too much). Let's see how it works and how it relates to the current "Tagless Final" trend