Clojurians Log v2

Hello, can you explain this macro code?

(defmacro inspect-caller-locals []
  (->> (keys &env)
       (map (fn [k] [`'~k k]))
       (into {})))

(inspect-caller-locals)
;;=>{}

(let [a 1 b 2] (inspect-caller-locals))
;;=> {a 1, b 2}

What do you need explained about it? &env is the environment the macro is evaluated in.

That's a variant of the local-map macro is the library that my company released a while back https://github.com/worldsingles/commons/blob/master/src/ws/clojure/extensions.clj#L152

^ @zengxh

consider local a and 1. in [`'~k k], if first element is 'a how does the second get value 1?

That's how macros work. Maybe this is a better question for #beginners ? I'm not sure where to start...

(I don't mean to be rude but I want to make sure we're started from the appropriate place)

No problem. 🙂

ah ok. captures.

Yeah, &env is magic but it's the captured environment by definition.

There's &form as well for the source form of the macro. Per https://clojure.org/reference/macros#_special_variables

thank you

I'm working on wrapping netty's http2 and I got stuck with this bit: https://netty.io/4.1/xref/io/netty/example/http2/helloworld/server/HelloWorldHttp2HandlerBuilder.html I was trying to use proxy to do the same thing (with my own reified handler of course), but I can't seem to get build to work properly.

(proxy [AbstractHttp2ConnectionHandlerBuilder] []
    (build
     ; ([] (proxy-super build))
     ([decoder encoder initial-settings]
      (let [handler (http2-handler decoder encoder initial-settings)]
        (proxy-super frameListener handler)
        handler))))