Hello, If a macro calculates something and wants to make that result available to the body, what's the right way to do that? So far I've tried these ways which don't work (this is not really my macro, it's just a simplified example to demonstrate the issue):
1) lexical scope doesn't work, the symbol gets qualified (defmacro test-it [addend & body] `(let [foo (+ ~addend 1)] ~@body)) => (test-it 3 (println foo)) CompilerException java.lang.RuntimeException: Can't let qualified name: fcms.app/foo, compiling:(NO_SOURCE_PATH:1:1) => (macroexpand '(test-it 3 (println foo))) (let* [fcms.app/foo (clojure.core/+ 3 1)] (println foo)) 2) autogen'ed lexical scope doesn't work, the body doesn't know what the autogen'ed symbol will be called (defmacro test-it [addend & body] `(let [foo# (+ ~addend 1)] ~@body)) => (test-it 1 (println foo)) CompilerException java.lang.RuntimeException: Unable to resolve symbol: foo in this context, compiling:(NO_SOURCE_PATH:1:12) => (macroexpand '(test-it 3 (println foo))) (let* [foo__5755__auto__ (clojure.core/+ 3 1)] (println foo)) 3) an interned var partially works, if the macro and its use are all in one namespace, but not if not, it fails to intern the var (defmacro test-it [addend & body] `(do (def foo (+ ~addend 1)) ~@body)) => (test-it 3 (println foo)) 4 nil => (macroexpand '(test-it 3 (println foo))) (do (def fcms.app/foo (clojure.core/+ 3 1)) (println foo)) => (ns test) nil test=> (fcms.app/test-it 3 (println foo)) CompilerException java.lang.RuntimeException: Can't create defs outside of current ns, compiling:(NO_SOURCE_PATH:1:1) I don't think my scenario is too unusual, but so far I haven't been able to find anything about how to best do this. It case it helps, the real macro is with-collection and it takes a collection name, does a lookup and some validation in a DB, then needs to share the collection's id with the body. Cheers, Sean -- -- 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.
