> As an aside, this doesn't look like a good use-case for macros >. You'd probably be better defining a map with keys for : > worker, :channel, etc. Either that or a protocol. Thank you much for your help. But I thought this is exactly what macros were for? In another language I would end up just copying-and-pasting the 4 defs, and then changing "update" to "remove" so I could have both an update channel and a remove channel. I thought that macros were suppose to be good at removing that kind of redundancy?
On Tuesday, December 10, 2013 12:53:31 PM UTC-5, James Reeves wrote: > > Remember that only the last form will be returned. So: > > (defn foo [] 1 2 3 4) > > will always return 4. The same principle applied with your macro. You > define four forms, but only return the last one. Instead, try wrapping all > the forms in a "do" block. > > As an aside, this doesn't look like a good use-case for macros. You'd > probably be better defining a map with keys for :worker, :channel, etc. > Either that or a protocol. > > - James > > > On 10 December 2013 17:42, larry google groups > <lawrenc...@gmail.com<javascript:> > > wrote: > >> I am working on web software where admins will be using HTML forms to >> update data in a MongoDb database. I decided to use Lamina to off-load >> the work to the background. There are several operations that need to >> happen: updates, deletions, etc, and I thought I'd put each on a different >> channel. So I tried to write a macro to generate the code needed for each >> of those channels. This was my first attempt: >> >> (defmacro establish-channel [action noun to-execute start-function-name] >> (let [channel-name (symbol (str "documents-to-" action "-in-" noun >> "-channel")) >> additive-action-name (symbol (str "add-to-" action "-channel")) >> worker-name (symbol (str action "-" noun "-worker"))] >> >> `(def ~channel-name (channel)) >> >> `(defn ~additive-action-name [document] >> (enqueue ~channel-name document)) >> >> `(defn ~worker-name [] >> (loop [document @(read-channel ~channel-name)] >> (~to-execute document) >> (recur @(read-channel ~channel-name)))) >> >> `(defn ~start-function-name [] >> (future (~worker-name)) >> (future (~worker-name)) >> (future (~worker-name)) >> (future (~worker-name)) >> (future (~worker-name))))) >> >> >> But in the repl, when I run this, and then I do this: >> >> user> (macroexpand-1 (establish-channel update mongo println >> start-mongo-channel)) >> >> I get: >> >> CompilerException java.lang.RuntimeException: Unable to resolve symbol: >> update-mongo-worker in this context, compiling:(NO_SOURCE_PATH:1:16) >> >> It seems to be complaining about this line: >> >> (future (~worker-name)) >> >> But I defined that function just above that line: >> >> `(defn ~worker-name [] >> >> So what could the problem be? >> >> -- >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clo...@googlegroups.com<javascript:> >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> clojure+u...@googlegroups.com <javascript:> >> For more options, visit this group at >> http://groups.google.com/group/clojure?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "Clojure" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojure+u...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
