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noprompt
meander
Clojure2019–2025
noprompt / meander

meander

Tools for transparent data transformation

Explore on GitHubRead Hacker News discussions
7Distinct people
9Mentions
0Explicit recommenders
986GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

Tools for transparent data transformation

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

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, 3:56:07 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 year9 dated mentions

Observed mentions: 2019-01-11 11:04:12 UTC to 2025-02-24 13:32:45 UTC.

01232019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 3 mentions; 1 submissions, 2 comments20192020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2022-01-01 00:00:00 UTC to 2023-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20222023-01-01 00:00:00 UTC to 2024-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2024-01-01 00:00:00 UTC to 2025-01-01 00:00:00 UTC (exclusive): 0 mentions; 0 submissions, 0 comments2025-01-01 00:00:00 UTC to 2026-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments2025

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

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC312
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC202
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC202
20222022-01-01 00:00:00 UTC2023-01-01 00:00:00 UTC101
20232023-01-01 00:00:00 UTC2024-01-01 00:00:00 UTC000
20242024-01-01 00:00:00 UTC2025-01-01 00:00:00 UTC000
20252025-01-01 00:00:00 UTC2026-01-01 00:00:00 UTC101

What Hacker News says

9 sources
erichocean·Feb 24, 2025
> There is no way to know what's being passed around without reading the source of the whole chain. But that's not what a Clojure dev would do. 1) We use Malli [0] (or similar) to check specs and coerce types if needed at every point. Checks can be left on in production (I do), or disable–up to you. 2) If the coercion is difficult, use something like Meander. [1] 3) If even that isn't straightforward and you need actual logic in the loop, use Specter. [2] 4) If you're not sure what going on at intermediate steps, use FlowStorm [3]. 5) But you're going to be processing a lot of data you haven't seen before! Use, Malli with test.check [4] and make use of property-based testing with generators. None of this is "advanced" Clojure, this is bread-and-butter stuff I use every day. 6) Need a Notebook-like experience to get better visualization of
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intermediate data? Use Clerk [5]. 7) Need special checks on API usage within your codebase? Use clj-kondo [6] with custom linters. They're less than 10 lines each. Unlike default-mutable languages, or typed, it's safe and easy to use libraries with Clojure and they tend to have very little churn. Total opposite from Python or JavaScript (if you're used to that). It's almost impossible to give the impression of what it is like to develop with Clojure if you've only ever used languages with static typing, or languages from the Algol family. Honestly, I hated Clojure's syntax at first BECAUSE I COULDN'T READ IT, and I loathed "structural editing." After 2-3 weeks, I read it just fine and it's hard to remember I ever couldn't do so. Now I like it, and structural editing makes it so easy to change your code, I couldn't live without it at this point. Basically, all my "fears"/dislikes were unfounded—it was a skill issue on my part, not a problem with Clojure. [0] https://github.com/metosin/malli [1] https://github.com/noprompt/meander [2] https://github.com/redplanetlabs/specter [3] https://www.flow-storm.org/ [4] https://github.com/clojure/test.check [5] https://clerk.vision/ [6] https://github.com/clj-kondo/clj-kondo
In Why Clojure?
keeeeeeeem·Oct 6, 2022
I can't speak to the quality of Zig's compile-time compilation, other than to comment and say the article is taking liberties with its use of the word unique. As other commenter's have noted, many languages have the feature. Instead I'm going to talk about a bunch of cool and weird compile-time code implemented by people much smarter than I. If anyone reading this is interested in compile-time computation, you owe it to yourself to read Paul Graham (of HN)'s own work on compile time programming, "On Lisp"[0], or to take compile-time ideas to the next level, Doug Hoyte's "Let Over Lambda"[1] (LOL). Lisp languages have a long and interesting history of compile-time computation via their various macro systems, and given the first-class inclusion in most Lisps, a greater variety of ideas have been explored regarding compile-time computation.
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A few interesting examples: LOL's "Pandoric macro"[2] lets you monkey-patch closure values. It's absolutely bonkers and would almost certainly be pathological to introduce to a codebase, but it's an example of pushing the boundaries of what's possible. Common Lisp's object system, implemented via macro[3]. To be honest, the entire Common Lisp language is a masterclass when it comes to learning about macros (I can't avoid mentioning Scheme's hygeinic macro system and Lisp-1/Lisp-2.) A special non-Lisp shout-out goes to Rust's Diesel library for embedding SQL DDL queries into macros[4] which is not something I've personally seen before. Clojure has a few interesting (and practical) macro libs, particularly core.async, which is an implementation of CSP (similar to Golang's channels AFAIK), it embeds perfectly into the existing language and extends its capabilities even though it's merely a library. Another interesting lib which comes to mind is Meander[5], which uses term-rewriting to provide transparent data transformations. Think declaratively interacting with data structures at compile time, and the library figuring out the best way of turning it into imperative value manipulation code. [0] http://www.paulgraham.com/onlisp.html [1] https://letoverlambda.com/ [2] https://letoverlambda.com/index.cl/guest/chap6.html#sec_7 [3] https://mitpress.mit.edu/9780262610742/the-art-of-the-metaob... [4] https://diesel.rs/ [5] https://github.com/noprompt/meander
In What Makes the Zig Programming Language Unique?
tekacs·Jul 17, 2021
I'll also leave these here, in case the conversation inevitably turns to pattern-matched function definition in Elixir. :) https://github.com/clojure/core.match -- pattern matching as a library https://github.com/killme2008/defun -- using core.match to implement Elixir/Erlang-like function definition https://github.com/noprompt/meander -- advanced pattern matching, for some fun and flavor :) What's also fun is that core.match is implemented using a paper from INRIA on how to efficiently convert patterns into decision trees: https://github.com/clojure/core.match/wiki/Understanding-the...
In Elixir protocols vs. Clojure multimethods
nerdponx·Apr 12, 2021
Sounds like declarative pattern matching which sounds just great to me [0]. I won't deny that XML sucks to write. But I'm not yet ready to throw the baby out with the bathwater. Maybe we keep using XML as a machine-readable serialization format (and XSLT as serialization of pattern-matching data transformations!) and people use native data structures in their own programming languages. Or we all switch to S-expressions. 0: https://github.com/noprompt/meander
In Traversing nested data-structures in various languages
emmanueloga_·Nov 16, 2020
I think rewrite is related to program transformation [1]? Most stuff that I've seen looks pretty academic, obscure, not very well maintained, etc ... Pure [2] is the only practical language I've stumbled upon that appears to be general purpose _and_ based on term rewrite. I wonder if XSLT could fall under this umbrella? It rewrites trees into other trees ... not sure if that's enough to be considered a term rewrite system. If yes, then maybe CDuce is also an interesting thing to check. The author of Ragel also has a program transformation system [4], but I'm not sure what state it is at, he seems to have been working on it for a long while but it doesn't seem to be something nearly as popular as Ragel. Edit: I think specter [5] and meander [6] also could be, perhaps tangentially, related to rewriting. Meander expressly mentions rewrite as
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inspiration/fondation. Curiously these two look a lil bit like xpath/xslt but with EDN as data model instead of XML infoset. -- 1: https://en.wikipedia.org/wiki/List_of_program_transformation... 2: https://github.com/agraef/pure-lang 3: https://www.cduce.org/#whatis 4: http://www.colm.net/open-source/colm/ 5: https://github.com/redplanetlabs/specter 6: https://github.com/noprompt/meander
In Exotic Programming Ideas, Part 2: Term Rewriting
tekacs·Sep 4, 2020
Specter is tremendously useful and rarely lets on a case where it can’t perform a transformation. For ensuring that you’re getting the most efficient form of a transformation [0] it’s incredible —- and it is somewhat data-oriented, allowing easy saving and reuse of navigators. Meander [1] is also wonderful. Its unification-based approach makes for nice expressions of intent. Its strategy-based approach to rewriting [2] is more flexible than most common walker libraries, too. [0]: https://github.com/redplanetlabs/specter/wiki/Specter's-inli... [1]: https://github.com/noprompt/meander [2]: https://github.com/noprompt/meander/blob/epsilon/doc/strateg...
In Specter – Clojure API for immutable programming (2017)

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