arrow-kt

arrow-meta

Kotlin2019–2021

arrow-kt / arrow-meta

arrow-meta

Functional companion to Kotlin's Compiler

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2Distinct people

5Mentions

0Explicit recommenders

405GitHub stars

REPOSITORY AT A GLANCE

What to know before exploring

What it is

Functional companion to Kotlin's Compiler

GitHub

Where it is used

No documented product use has been verified yet.

What people are saying

No recommendation phrase was found in the indexed comments.

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Also in these discussions

kotlin/keep · linked in 2 of the same discussions

Mentioned in the same Hacker News threads. That is not proof they are substitutes.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by month5 dated mentions

Observed mentions: 2019-12-07 14:31:15 UTC to 2021-03-24 02:26:53 UTC.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges

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Period	Start (UTC)	End (exclusive, UTC)	Mentions	Comments
Dec 2019	2019-12-01 00:00:00 UTC	2020-01-01 00:00:00 UTC	1	1
Jan 2020	2020-01-01 00:00:00 UTC	2020-02-01 00:00:00 UTC	0	0
Feb 2020	2020-02-01 00:00:00 UTC	2020-03-01 00:00:00 UTC	0	0
Mar 2020	2020-03-01 00:00:00 UTC	2020-04-01 00:00:00 UTC	0	0
Apr 2020	2020-04-01 00:00:00 UTC	2020-05-01 00:00:00 UTC	0	0
May 2020	2020-05-01 00:00:00 UTC	2020-06-01 00:00:00 UTC	1	1
Jun 2020	2020-06-01 00:00:00 UTC	2020-07-01 00:00:00 UTC	0	0
Jul 2020	2020-07-01 00:00:00 UTC	2020-08-01 00:00:00 UTC	0	0
Aug 2020	2020-08-01 00:00:00 UTC	2020-09-01 00:00:00 UTC	1	1
Sep 2020	2020-09-01 00:00:00 UTC	2020-10-01 00:00:00 UTC	0	0
Oct 2020	2020-10-01 00:00:00 UTC	2020-11-01 00:00:00 UTC	0	0
Nov 2020	2020-11-01 00:00:00 UTC	2020-12-01 00:00:00 UTC	0	0
Dec 2020	2020-12-01 00:00:00 UTC	2021-01-01 00:00:00 UTC	0	0
Jan 2021	2021-01-01 00:00:00 UTC	2021-02-01 00:00:00 UTC	0	0
Feb 2021	2021-02-01 00:00:00 UTC	2021-03-01 00:00:00 UTC	0	0
Mar 2021	2021-03-01 00:00:00 UTC	2021-04-01 00:00:00 UTC	2	2

What Hacker News says

5 sources

The_rationalist·Mar 24, 2021

Thanks for the example, that's interesting. Note that Kotlin has union types through this compiler plugin: https://github.com/arrow-kt/arrow-meta/issues/570 However it is experimental and shouldn't yet be used in production. Btw sealed classes take care of many uses of union types. What kind of extra work is needed? I'd say that graal native is transparant for any library that doesn't do weird use of reflection but it's true that many libraries do abuse of reflection.

In Crystal 1.0 – What to expect

The_rationalist·Mar 16, 2021

Kotlin has this amazing concept called compiler plugins where you can extend, intercept and alter the compiler at any stage of the compilation pipeline (ast, psi, ir) through an API. There even are frameworks that make writing such plugins easier such as https://github.com/arrow-kt/arrow-meta (which enable to bring union type, higher kinded types, pattern matching, etc) Or https://github.com/google/ksp

In Kotlin Compiler Crash Course

The_rationalist·Aug 18, 2020

Arrow meta is a compiler extension that will bridge the gap even more e.g by bringing union types https://github.com/arrow-kt/arrow-meta

In Kotlin 1.4

The_rationalist·May 28, 2020

Nim compiles to JS both directly, and indirectly (emscripten) with various trade-offs (e.g. 64 bit ints require emscripten) Kotlin can also compile to js directly and can autogenerate typescript definitions for the generated code. It also compiles to C, C++ and Objective C giving you the simplest most efficient FFI to those languages one can hope for (including e.g. exception handling) while at the same time addressing the largest set of platforms (got a C compiler? you can use Nim). Wow, nim has implemented that much transpilers? This is kinda impressive but I would rather want a language that compile to Binary instead of compiling to another language, AND that offer nice FFI interop Kotlin has state of the art language interop through graalvm but here it does not qualify as native. For native interop it can be done but is subpar. But o

Read the rest

penjdk is working on a new API luckily. Metaprogramming Interesting topic for sure! I've never learnt a LISP. I did use macros when I was doing C/C++ and honestly I don't get their advantages vs @Decorators() (pre compile time codegen) and they have a reputation of breaking IDEs Kotlin like Java can generate code/classes at runtime and has full support for reflection. Tangeant: Kotlin can mark any function as in/postfix which allows to easily create DSLs. Due to this Kotlin community has created a lot of elegant, declarative DSLs such as for testing. Nim's async support (comparable to Python and C#) is a user-level library. Kotlinx.coroutines is the official library the language simply has to expose the keyword suspend. So is, for example, pattern matching. Can Kotlin do that? Kotlin has some pattern matching features in its when keyword,but no it cannot currently destructure in when. But the subject is active and it should come in a following release, especially since Java is getting pattern matching. https://github.com/Kotlin/KEEP/pull/213 But if your point was that macros allows to modify the abstract syntax tree, Kotlin compiler plugin API offer much more power (you can modify anything anytime (the AST, the IR, the bytecode) It is arguably far harder to use than powerful macro but it does not prevent experimented guys from scalaifying Kotlin through https://github.com/arrow-kt/arrow-meta/issues They are bringing for example union types as an unofficial extension to the language. They could bring pattern matching earlier in theory. Size: Nim compilation through C produces standalone and (relatively) tiny executables; it matters for embedded platforms. How does Kotlin fair in this respect?* I'm afraid kotlin is not made for such a use case but today even embedded platforms should have a few dozens of free MBs

In Pros and Cons of Nim

adimitrov·Dec 7, 2019

Java will not get HKTs in yours and my lifetime. What might get HKTs is Kotlin. There's a proposal brought forward by the Arrow people that has attracted a lot of attention. https://github.com/Kotlin/KEEP/pull/87 If if that does not succeed, the Arrow folks are working on a meta compiler (think template Haskell but with IDE support) that should get you HKTs and union types. https://github.com/arrow-kt/arrow-meta Regardless, something quite close to HKTs is available today via type level defunctionalisation. Just look at the Arrow docs

In The Road to Valhalla