On Monday, April 1, 2013 10:26:43 AM UTC-7, Alf wrote: > I am guessing the problem is that the rethrow macro is expanded and passed > to the reader/compiler before the handle-ex macro is. And at that point the > compiler sees catch as a "standalone-symbol", not as part of the try > special form. Macro-experts, please correct me :) > > Tried to quickly catch up with > http://www.infoq.com/presentations/Clojure-Macros, but infoq seems slow. > > On 1 April 2013 17:21, Bill Robertson <billrob...@gmail.com > <javascript:>>wrote: > >> I was all excited when I was able to consolidate a lot of try/catch logic >> behind a macro earlier this morning. All was good. >> >> I felt like I could do a better job of communicating my intentions in the >> code though with a rethrow construct rather than writing >> (catch FooException #f (throw #f)) >> >> I would have liked to have been able to simply write >> (rethrow FooException) >> >> This failed. Poking around the docs a bit, I see that try/catch is a >> special form. Which makes sense. >> >> user=> (defmacro rethrow [ex-class] `(catch ~ex-class x# (throw x#))) >> #'user/rethrow >> user=> (defmacro handle-ex [message & body] `(try ~@body (rethrow >> IllegalArgumentException) (catch Exception x# (throw >> (IllegalArgumentException. message))))) >> #'user/handle-ex >> user=> (handle-ex "no" (throw (IllegalArgumentException. "yes"))) >> CompilerException java.lang.RuntimeException: Unable to resolve symbol: >> catch in this context, compiling:(NO_SOURCE_PATH:1:1) >> >> It was a longshot, but I tried to qualify catch. That fails too, because >> it's not really there... >> >> user=> (defmacro rethrow [ex-class] `(clojure.core/catch ~ex-class x# >> (throw x#))) >> #'user/rethrow >> user=> (defmacro handle-ex [message & body] `(try ~@body (rethrow >> IllegalArgumentException) (catch Exception x# (throw >> (IllegalArgumentException. message))))) >> #'user/handle-ex >> user=> (handle-ex "no" (throw (IllegalArgumentException. "yes"))) >> CompilerException java.lang.RuntimeException: No such var: >> clojure.core/catch, compiling:(NO_SOURCE_PATH:1:1) >> >> Is this possible to do within the normal bounds of the language? >> >> Thanks! >> >> >> -- >> -- >> 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. >> >> >> > > That is the opposite of the problem: `try` searches for a `catch` without macroexpanding its body forms. You could come at the problem differently, by writing a macro that expands to an entire try+catch form: (try-rethrowing [IllegalArgumentException] (do a b c) (catch Exception e e) (finally (foo))) is a macro that you could successfully write.
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