On Dec 6, 9:22 pm, Allen Rohner <aroh...@gmail.com> wrote: > > What is it supposed to do? What's the usage look like? > > Oh right, a description would be useful. The point is to build up the > functionality of a function from several places. You define a hook > function: > > (defhook foo [a b]) > > Initially, it does nothing. Then, other code can add hooks: > > (add-hook foo :first-hook (fn [a b] (println "first!"))) > > The hooks should all have the same signature as in defhook. You can > add as many as you like. The second argument is a "name", so you can > remove the hook later if desired. > > (add-hook foo :second (fn [a b] (println "a=" a "b=" b))) > > Then, call the function, and all of the hooks get called in the order > added > > user> (foo 1 2) > first! > a= 1 b= 2 > nil > > There's also a function, remove-hook, that works about the way you'd > expect. > (remove-hook foo :first-hook) > > > Why does defhook's signature arg never get used? > > It'd also help readability to wrap your doc string. > > This is just a sketch. I meant for the signature to go into the > arglist metadata of the def'd var, but couldn't get it to work in 5 > minutes, and gave up on it (for now). I plan on doing all of that > polishing, assuming nobody tells me it's not evil. Honestly, I'm not > sure yet, but it seems to work well for Emacs, and I couldn't think of > a better alternative for my own Clojure problem. > > Allen
Hmm. A few observations: - You can only compose side-effect-only functions that can't interact with each other. I could see that being useful for stuff like trace logging, but even in those cases there's an initial function with its own utility (and returne value). This is basically a loosely constructed do block. - The behavior is a bit "magical" as regards to who adds stuff, though I guess that's not too different from defmulti. - Maps vs vector-of-vector, dealing with duplicate identifiers, etc. What was the actual usage scenario that drove this? -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
