On the Clojurians Slack, PEZ brought some delicious Fibonacci performance tuning from the “languages” repo. While I don’t think that benchmark is as useful as mesmerizing the moving circles are in the animated graphs, I had a few very confusing and interesting discoveries.
Step 1: watch Alex Miller’s talk about Clojure’s interop performance. Step 2: learn how to actually do all that stuff. Step 3: notice that recursion does things. Step 4: magic.
Working on a Chrome plugin I got to use ClojureScript in yet another new environment. After the usual browser setup, Node, Deno and Github Actions, this time it was the Chrome plugin system. While it was mostly a very smooth ride, I had a little trouble figuring out how to deal with a “Cannot infer target type in expression” warning.
It showed up while dealing with a HAR entry object passed in to my callback from devtools.network.onRequestFinished. The HAR object, while its shape is well defined, is not typed in a strict sense (though I guess there may be some type definition for it somewhere out there if I looked hard enough). That’s why when I tried to access its fields like (-> entry .-request .-url) the ClojureScript compiler (through Shadow CLJS) would complain about inferring the “target type” as above.
やりたかったことは多言語対応の一環だった。flutter_localizationsの生成コードでBuildContextからAppLocalizationは取得できるが、それと別にOSの言語設定を監視したかった。そのために他のウィジェットを包むだけのものを用意して、ミドルウェア的な挙動でOSの言語設定をアプリのDBに保管したかった。でもなぜかそれを適応すると、今度はgo_routerのStatefulShellRouteを使った遷移が機能しなくなってしまった。
If you’ve worked with Mastodon (or possibly other ActivityPub implementations too) HTTP Signatures might sound familiar. When notifying another server of an event, the request can be signed thus proving its authenticity, meaning that the receiving server doesn’t need to go and fetch the authoritative version from the origin. This reduces load on both the receiver of the event (less requests to send) and the origin (less requests to serve).
Clojureでプロトコルをよく使う。defprotocolで作ってextend-protocolで各種の型に実装すると、いろんな入力値にスムーズに対応できる。例えば暗号化周りで、ハッシュや署名の算出のためにバイト配列が必要な際、プロトコルを活かしていい感じのAPIが提供できる。
(defprotocol Byteish
(->bytes ^bytes [input]))
(extend-protocol Byteish
String
(->bytes [input] (.getBytes input)))