The following code may prove useful as well. (defmacro log "for debugging, output code and code->val to stdout or optional writer, returns val, custom-fn accepts two arguments, the code, and the result, it must return a string" ([code] `(let [c# ~code] (prn '~code) (clojure.pprint/pprint c#) c#)) ([code writer custom-fn] `(let [c# ~code w# ~writer] (.write w# (~custom-fn '~code c#)) (.flush w#) c#)))
(defn- add-log-calls [code] (if (seq? code) `(log ~(map add-log-calls code)) code)) (defmacro r-log [code] (add-log-calls code)) The log prints the form and its output. r-log recursively wraps all calls (symbols wrapped in parens), with the log macro. r-log stops printing where when the form fails. Also you'll be able to see what the passed values between functions are. On Aug 2, 6:35 pm, recurve7 <dan.m...@gmail.com> wrote: > Hi Jeremy, > > I'm not just thinking about Clojure from the perspective of a Java > person, but also from the perspective of someone new to programming > and for kids. For the latter, it's best if languages have maximum > friendliness in error wording and error messages pointed at a specific > character position on a line, which is common in many languages now. > > On Aug 2, 6:53 am, Jeremy Heiler <jeremyhei...@gmail.com> wrote: > > > > > > > > > On Tue, Aug 2, 2011 at 3:11 AM, recurve7 <dan.m...@gmail.com> wrote: > > > Here's one example where recursion and lack of positional error > > > feedback make it hard for me, as someone coming from Java, to spot the > > > error (and seeing "ClassCastException" threw me off and had me > > > wondering where/how I had done something like that): > > > > user=> (defn fac [n] (if (= n 1) 1 (* n fac (- n 1)))) > > > #'user/fac > > > user=> (fac 3) > > > java.lang.ClassCastException: user$fac cannot be cast to > > > java.lang.Number (NO_SOURCE_FILE:0) > > > What were you thoughts *before* you asked Google? > > > As being someone who is also coming from Java, this error message > > seems fairly clear. You've used `fac` when it expects a number. Now, > > assuming you know how `defn` works, it must be the second instance of > > `fac` that is causing the issue. Then, since it's expecting a number, > > assume it is, and then ask yourself why it wouldn't complain if it was > > a number. Then go from there. > > > Also, keep in mind you're in the REPL, where line numbers aren't all > > that useful. -- 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