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Comment by eru | Hacker News Reader

FP ideas have been seeping into the mainstream for quite some time now.

The oldest: GC was originally invented for Lisp. It's common now.

Type inference was big in FP before it made the jump to language like Java or C++ much more recently.

Generics were a natural idea in a typed FP context. Mainstream languages got them, now.

I'm looking forward to algebraic data types becoming really common. (The simplest explanation is that they are C-style unions with tags to tell you which case you are in. The compiler enforces that the tags correspond to how you use them.) Some mainstream languages are starting to add them.

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> The oldest: GC was originally invented for Lisp. It's common now.

LISP was so ahead of its time, its parents still haven't met yet. Not very FP, but another gem from SBCL: saving and restoring program state for later use. Now there's the CRIU [0] project for doing this with Linux and Docker containers.

> I'm looking forward to algebraic data types becoming really common.

I'm not too familiar with the full scope of algebraic data types. Wondering: does Typescript have this or is it still missing a few key components? Really like how it has Union types, which I wish Scala would have.

[0] https://www.youtube.com/watch?v=LrHW7Vvbie4

Algebraic data structures mostly just means union types.

(That's the + in the algebra. The * comes from bundling multiple values together, like in a tuple or in a C-style record, virtually all languages already have that.)

There's also Generalized Algebraic Datatypes (GADT). They are a bit more complicated. So I don't expect mainstream languages to pick them up anytime soon.

About GC: you _can_ do pure functional programming without a GC. But it requires lots of big guns from more advanced theory. (Mostly stuff like linear typing.) However imperative programming without a GC is comparatively simple.

So it's no wonder that historically, GC was invented for FP first, and GC-free FP was only discovered later.

(And for general CRUD or web programming, or basically anything outside of low level systems programming, GC is more productive in terms of programmer time than other approaches. At least given currently known techniques.)

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