2011/1/25 Ken Wesson <kwess...@gmail.com>: > Are we generally agreed that we want to preserve the body exception, > if any, else the close exception, if any, else the body return value? > > Then, without further ado: > > (defmacro with-open2 [binding-exprs & body] > (if (> (count binding-exprs) 2) > `(with-open2 ~(vec (take 2 binding-exprs)) > (with-open2 ~(vec (drop 2 binding-exprs)) > ~@body)) > (let [[sym expr] binding-exprs] > `(let [~sym ~expr > res# (try > [(do ~@body)] > (catch Throwable t# t#))] > (if (vector? res#) ; body didn't throw > (do > (.close ~sym) ; so let close throw > (res# 0)) > (do ; body threw > (try (.close ~sym) (catch Throwable _#)) ; eat close exception > (throw res#))))))) ; and rethrow body exception > > user=> (with-open [x (Foo.)] (doit x)) > #<CompilerException java.lang.Exception: close exception (NO_SOURCE_FILE:242)> > user=> (with-open2 [x (Foo.)] (doit x)) > #<CompilerException java.lang.Exception: doit exception (NO_SOURCE_FILE:40)>
What about starting from the current definition of with-open in clojure.core, improving upon it (and at the same time, not building intermediate wrapper vector) : (in-ns 'clojure.core) (defmacro with-open "bindings => [name init ...] Evaluates body in a try expression with names bound to the values of the inits, and a finally clause that calls (.close name) on each name in reverse order." {:added "1.0"} [bindings & body] (assert-args with-open (vector? bindings) "a vector for its binding" (even? (count bindings)) "an even number of forms in binding vector") (cond (= (count bindings) 0) `(do ~@body) (symbol? (bindings 0)) `(let ~(subvec bindings 0 2) (try (let [res# (with-open ~(subvec bindings 2) ~@body)] ;body didn't throw (. ~(bindings 0) close) res#) (catch Throwable t# (try (. ~(bindings 0) close) (catch Throwable _)) ; eat close exception (throw t#)))) ; and rethrow body exception :else (throw (IllegalArgumentException. "with-open only allows Symbols in bindings")))) -- 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