Clojure on Fennel Part One: Persistent Data Structures (andreyor.st)

by roxolotl 21 comments 165 points
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21 comments

[−] xeubie 35d ago
Clojure's immutable HAMTs are still a superpower nearly 20 years later. They've been copied in pretty much every language as a library (I did so myself in Zig) but what really makes it work well in Clojure is the fact that they're built into the language, so the entire ecosystem is built around them. Libraries that were made independently usually fit together like a glove because they are all just maps/vectors in -> maps/vectors out.
[−] slowmovintarget 35d ago
HAMT -> Hashed Array Mapped Trie for those wondering.

https://en.wikipedia.org/wiki/Hash_array_mapped_trie

(The acronym is expanded in the article, but a ways down.)

[−] dapperdrake 35d ago
I thought it cheesy at the time. Then I tried clojure.

"The value of values". Indeed. Q.e.d. No notes.

[−] packetlost 35d ago
Yeah. I do wish there was something that was like Clojure with a TypeScript or Go-like nominal typing, but I do feel myself missing types a lot less with Clojure compared to other languages.
[−] gsk22 34d ago

> Libraries that were made independently usually fit together like a glove because they are all just maps/vectors in -> maps/vectors out.

This is also the biggest weakness of Clojure (IMO). When everything is "just data", you spend a lot of time digging deep in libraries trying to figure out exactly what shape the data should take. Additionally, the shape of input data is almost never validated, so you spend lots of time debugging nasty type errors far from the place where bad data entered the program.

There have been some abortive attempts at solving this with things like spec, Prismatic Schema, etc, but nothing that has taken hold like TypeScript did with JS.

I'm still waiting for my dream language with the flexibility and immutability of Clojure, but without the pain points of an anything-goes attitude towards typing and data shape.

[−] kgwxd 34d ago
I think I know and love more about clojure than any language I actually use.

I rewatch hickey talks anytime Im a little stuck on a big problem/idea and there's almost always another "ah ha" moment for me.

If the places i work were already on the JVM, i would have switched a decade ago, but I've been in .net world my whole career.

[−] iLemming 35d ago
Yeah, they are so underappreciated - the practical differences in designing, delivering and maintaining software are real. Initially you see small differences "What's the point? I can write that in Python too... maybe it's not as delightful, but who cares?...", etc. Yet over time small annoyances accumulate and become an endless stream of headaches. I see it over and over again - I work on a team where we have codebases in different languages, and some services written in Clojure. Immutability by default is a game of a different league.
[−] bjoli 34d ago
Didnt they move to CHAMP? Otherwise, that seems like a waste of resources. They are literally the same but CHAMPs are a little faster in just about every way.

I am still a bit disappointed that they didn't change to RRB trees or copy the scala vectors instead of the built in ones. Iirc the scala vectors are faster in general while providing a bunch of benefits (at the cost of code complexity though, but even a better RRB list implementation instead of the scala finger trees would allow for that).

I wrote an RRB tree implementation in c# just for fun [0], and while they are harder than the tries of clojure, the complexity is pretty well contained to some functions.

0: https://github.com/bjoli/RrbList/tree/main/src/Collections

[−] devnotes77 35d ago
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