The Purpose of Functional Programming

You have to have universal composition as a guarantee, otherwise you're going to screw up. And the effect is the way to encapsulate that. If you don't have a single way of encapsulating that, it's just another of time you'll be two things that don't talk to each other well. So would you say that composability is maybe the whole reason for functional programming? "The programmer wants to write the what, what they should do"