I haven't read the article in depth, but the authors example is written according to SOLID principles where composition is decoupled via interfaces and dependen

I haven't read the article in depth, but the authors example is written according to SOLID principles where composition is decoupled via interfaces and dependency injection. I think the author is trying to show the difference between highly decoupled code examples in c# and f#. In f# you compose with functions, in c# you compose with object instances.