> I consider [having a big benefit at 100% vs an 80/20 rule] a characteristic of type systems in general; a type system that you can rely on is vastly more useful than a type system you can almost rely on, and it doesn’t take much “almost” to greatly diminish the utility of a given type system.

This! This is why I don't particularly care for gradual typing in languages like Python. It's a lot of extra overhead but you still can't really rely on it for much. Typescript types are just barely over the hump in terms of being "always" enough reliable to really lean on it.

I mostly agree with the sentiments in this article. I was once an extremely zealous FP acolyte but eventually I realized that there are a few lessons worth taking from FP and applying to more conventional programming: 1. Pure functions are great to use when you have the opportunity. 2. Recursion works great for certain problems and with pure functions. 3. Higher order functions can be a useful shorthand (but please only use them with pure functions). Otherwise, I think simple, procedural programming is generally a better default paradigm.

I was hoping this article would be a little more concrete, but it seems that it largely is talking about the takeaways about functional programming in a philosophical, effort-in vs value-out kind of way. This is valuable, but for people unfamiliar with functional programming I'm not sure that it gives much context for understanding.

I agree with the high-level, though. I find that people (with respect to programming languages) focus far too much on the specific, nitpicky details (whether I use the `let` keyword, whether I have explicit type annotations or type inference). I find the global, project-level benefits to be far more tangible.

I've always thought that there should be mutability of objects within the function that created them, but immutability once the object is returned.

Ultimately one of the major goals of immutability is isolation of side effects.

Note that this post is the end of a larger series of posts, collected in one page here: https://jerf.org/iri/blogbooks/functional-programming-lesson...