ErlangはEricssonがはるか昔に開発した通信環境用の言語で、ものすごく頑丈で安定している環境として有名。実際に世界中のモバイル通信環境で用いられ99.9999999% (“nine nines”) の可用性を誇っている。最近ではRuby風でErlangのBEAMを実行環境とするElixirが流行っている印象がある。分散を前提にしている関数型言語としてClojureに近いと感じた。そして実際にBEAMの上でClojureを実装しているものがある。
Clojureが最初はJVMと.NETのCLRも対象にしていたが後JVMだけになり、またClojureScriptの登場でJavaScript上で動くようになった。だから根本的なところは案外実行環境に依存しないところもあるかもしれない。BEAM上でClojureを実装しているClojerlはあくまでもコミュニティーからのもので正式なClojure版ではないが、試したかったBEAMと選べるなら選ぶぐらい好きなClojureが合ったものに当たるから触ってみざるをえなかった。
Was trying to figure out what
zerusski on Clojurians Slackdefrecorddoes in the impl of ILookup it generates and I absolutely do not understand that magic. Essentially it amounts to(get __extmap key)and I can’t even figure out how this magical__extmapgets into scope (a global or some special runtime thing?) andthisisn’t even used. Confused
This post on Clojurians sent me down the rabbit hole looking for where this “mysterious” __extmap comes from. It really isn’t obvious at first, but when I found it, it was “wow” times “duh”.
以前gitのGUI作りたいと思っていろんな試行錯誤して落ち着いたのはClojureScript（re-frame使ったReact）とElectronで作ったUIにRustのgit2-rsで生のgitとのやりとりする方式。まだちょっとややこしいところも残っているが、ほとんどはそれなりにスムーズな開発フローに乗れた。
The past week or so I’ve been working on implementing the QUIC protocol in Clojure. Currently there is no Java implementation to use either (that I know of), and I just found out the other day that netty decided to use the Cloudflare’s Rust library quiche under the hood instead of rolling their own. The protocol is currently a IETF draft at version 32, expected to turn into an RFC soon.
It’s been a year since I wrote about bootstrapping a cluster with Argo and using Argo Rollouts for canary deploys based on Prometheus metrics. Since then many things have changed. I moved from Digital Ocean to Linode (mostly because Linode has a Tokyo region) and from a single-node k3s “cluster” to a 4-node one. But most of how I use Argo CD for GitOps hasn’t changed.
Java 8 came out in 2014 and brought along functional interfaces. Functional in general just means that you can treat functions (or methods) as “things” instead of having no proper way to talk about them. In this sense Javascript for example is functional: you can pass around functions all you want. Java’s had Runnable and Callable that are pretty similar in concept.
Then came Java 8 and with it the “mighty arrows.” For some reason Ruby, Javascript and Java all opted to use the same bit of syntax to talk about lambdas (anonymous functions): ->. In Ruby it’s ->(foo) { foo }, in Javascript it’s (foo) -> foo, and surprisingly in Java it’s the same. Run a few rounds with futures and/or streaming stuff and you’ll definitely want to pass such a lambda to forEach for example.
Next up in the series complaining about Clojure’s Java interop is proxy. While vararg method calls are inconvenient at worst, there are some (I’d say common) things that simply cannot be achieved with proxy.
Once again this is something I ran into while working with Netty. In one of the HTTP/2 examples, they have one implementation extending AbstractHttp2ConnectionHandlerBuilder<T, B> (have I mentioned I find these extremely long Java class names just hilarious?). The Java implementation is pretty straightforward: implement the abstract method of the class and be done with it.
Variable length argument lists (varargs) have been around since Java 5 (so quite a long while), yet I get the impression that many people either don’t know about this feature or their tools don’t support it. I ran into one of them working with Netty from Clojure and it wasn’t trivial at all how to use them through interop.
Ran into this issue in a programming challenge on HackerRank and I was surprised there weren’t any “simple” solutions online. The math related is mostly focused on finding the number of possible partitions of an integer, instead of generating even just one such partition.
A very naive approach might be to enumerate all partitions and then filter them down to those with exactly the wanted number of summands and then filter further to those with distinct parts and pick the first that fulfills the conditions.
But when the subject integer can be 1018 then that simply isn’t realistic. Insert sophisticated simile involving the heat death of the universe.
Honing your skills on CodeWars or HackerRank is definitely a good idea. I’ve myself spent months on the former and some time on the latter, and right there is a display of my issue with them: I lose interest. At first it’s really nice to tackle a bunch of “interesting” problems and feel successful, but as the difficulty of the problems goes up, it soon turns into “how do I get around the shortcomings of the language I use?”
That’s naturally something worth considering, but it just feels so weird when I have to overcome performance tests aimed at C in Ruby (or Clojure). It’s doable (most of the time), but it’s a whole different kind of measure. I recall a problem for which solutions in C were mostly pretty naive loops while something similar in Ruby would fail even the first few load tests.