Modern Functional Programming: The Onion Architecture
Gary Bernhardt describes a similar architecture using a "Functional Core, Imperative Shell" in his Boundaries talk[1].<p>"Purely functional code makes some things easier to understand: because values don't change, you can call functions and know that only their return value matters—they don't change anything outside themselves. But this makes many real-world applications difficult: how do you write to a database, or to the screen?"<p>"This design has many nice side effects. For example, testing the functional pieces is very easy, and it often naturally allows isolated testing with no test doubles. It also leads to an imperative shell with few conditionals, making reasoning about the program's state over time much easier."<p>[1] <a href="https://www.destroyallsoftware.com/talks/boundaries" rel="nofollow">https://www.destroyallsoftware.com/talks/boundaries</a><p>[2] <a href="https://www.destroyallsoftware.com/screencasts/catalog/functional-core-imperative-shell" rel="nofollow">https://www.destroyallsoftware.com/screencasts/catalog/funct...</a>