Help me sort out the meaning of “{}” as a constructor argument • Hacker News Board

Post by jholman » Wed, Nov 30, 2016, 5:42 AM UTC

Pyxl101 wrote: post #162

jholman wrote: post #161

Earlier quoted context omitted.

I'm confused that you seem to think that "FP" means immutability. I think that most lisps and schemes, for example, have had mutable state. ML does. I think APL does? I think Erlang does, even though it says it doesn't? It's just a few Johnny-come-lately languages that do this immutability-is-the-default thing. Heck, even Clojure doesn't commit to it. Although I agree that lots of them discourage the use of mutabilit…

Functional Programming as I've always heard the term defined is the style of programming that avoids mutable state in favor of computation over immutable data structures. From Wikipedia: > In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. https://en.wikipedia.org/wiki/Functional_programm…

I've seen the WP page. If that's what FP is, then I think that means that either

  * think Lisps and Schemes aren't true FP, or
  * think that Lisps and Schemes avoid mutable state

Which one of those is your belief? I'm not a serious user of any allegedly-FP language, so maybe I misunderstand the history of FP. Note that I concede that Lisp seems to be less obsessed with mutating state than most procedural languages, but I think saying that it "avoids" it is an overreach.

Of course, some people could claim that "old" FP languages like Lisp and Scheme aren't truly FP.

As for your definition of OO, I think the word that describes abstraction across various instance-types is "polymorphism". That's when code can be written that handles multiple types, either because the typing system allows it, or because the typing system is so flexible that it fails to forbid it. Functional code is usually highly polymorphic, whether it's an aggressively static type system (Haskell with type classes) or an aggressively late-binding dynamic type system (typical Lisp, before anyone bothered to invent the phrase "duck typing").

Again, the central concept of OO, at least according to Alan Kay (the inventor/definer of the term), who said in 2003 (later than other definitions of his I could find) "OOP to me means only messaging, local retention and protection and hiding of state-process, and extreme late-binding of all things." I think it's pretty clear that statefulness is pretty essential to that definition.

http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/doc_kay...