The backtick namespace-qualifies symbols automatically: (macroexpand-1 '(switch-foo-library! x)) ;=> (clojure.core/defn user/foo [y__3652__auto__] ((clojure.core/resolve (clojure.core/symbol (clojure.core/str x "/foo"))) y__3652__auto__))
The error is about the "user/foo" name of the defn. You can fix this by quoting the symbol then immediately unquoting it: (defmacro switch-foo-library! [x] `(defn ~'foo [y#] ((resolve (symbol (str ~x "/foo"))) y#))) ;=> #'user/switch-foo-library! (macroexpand-1 '(switch-foo-library! x)) ;=> (clojure.core/defn foo [y__3946__auto__] ((clojure.core/resolve (clojure.core/symbol (clojure.core/str x "/foo"))) y__3946__auto__)) However what you really want probably something with with-redefs <http://clojure.github.io/clojure/clojure.core-api.html#clojure.core/with-redefs> : (defmacro with-ns [ns vars & body] {:pre [(symbol? ns) (nil? (namespace ns)) (every? #(and (symbol? %) (nil? (namespace %))) vars)]} (let [bindings (vec (mapcat #(do [% (symbol (str ns) (str %))]) vars))] `(with-redefs ~bindings ~@body))) ;=> #'user/with-ns (ns alt) ;=> nil (def juxt (constantly (constantly "NEW JUXT"))) ;WARNING: juxt already refers to: #'clojure.core/juxt in namespace: alt, being replaced by: #'alt/juxt ;=> #'alt/juxt (in-ns 'user) ;=> #object[clojure.lang.Namespace 0x77b2abef "user"] (with-ns alt [juxt] (map (juxt :a :b) (repeat 4 {:a 1 :b 2}))) ;=> ("NEW JUXT" "NEW JUXT" "NEW JUXT" "NEW JUXT") ((juxt :a) {:a 1}) ;=> [1] If you want to make the var change permanent (i.e. not requiring your body be inside with-redefs), you can use alter-var-root <http://clojuredocs.org/clojure.core/alter-var-root>, but you have to take care to allow the vars to be restored somehow, e.g. by storing the old mappings somewhere and providing a macro to save and restore them. It's possible someone has scratched this itch before, too: there might be a utility library out there somewhere that does something like this. On Tuesday, April 5, 2016 at 9:10:15 PM UTC-5, Will Bridewell wrote: > > I'm working on some code where I want to evaluate different > implementations of the same functionality. Each implementation of a > function lives in its own namespace. For example, suppose that I have the > following simplified code. > > (ns tst1) > (defn foo [x] (+ x 1)) > > (ns tst2) > (defn foo [x] (+ x 2)) > > (ns tst3) > (defn foo [x] (+ x 3)) > > (in-ns 'user) > > What I'd like to do is call a macro that binds the function name in user > to the function in one of the libraries. The call would look like one of > these. > > (switch-library! 'tst1 'foo) > > (switch-foo-library! 'tst1) > > The closest that I got was to do > > (defmacro switch-foo-library! [x] > `(defn foo [y#] ((resolve (symbol (str ~x "/foo"))) y#))) > > That's kind of embarrassing, but I think it does what I want. However, > suppose I do > > (ns-unmap 'user 'juxt) > (defmacro switch-juxt-library! [x] > `(defn juxt [y#] ((resolve (symbol (str ~x "/juxt"))) y#))) > > Now I get > > CompilerException java.lang.RuntimeException: Can't create defs outside > of current ns, compiling: > > Well, gosh. I can't play around with symbols in clojure.core? What's > happening here? > > > -- 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/d/optout.
