On Dec 3, 2008, at 7:19 PM, aria42 wrote: > Hi all, > When I run the following from the REPL, I see the result of the > "println" > > (defn read-docs [duc-dir] > (for [file (.listFiles (java.io.File. duc-dir)) > :when (.isFile file)] > (do > (println file) > (.getName file)))) > > > However, when embedded in a script (using clojure.lang.Script), I > don't see the result of the println. I'm primarily using it for > debugging the compreshension variables. > > Thanks a lot, Aria
Hi Aria, The result returned by the "for" function is a lazy sequence. It will only produce as many values as are actually requested by its caller. In the case of the repl, the "print" part of the read-eval-print-loop will force it to produce all the results. In the case of Script, there is nothing to force the output, so it will never be produced and println won't be called. If your primary goal is the side-effect produced by "println", doseq (which has recently been upgraded to be a complete non-lazy counterpart to "for") should do the trick. Just drop it in in place of "for". (it will ignore the result returned by (.getName file) in that case, so that can and should be removed.) Another way to do this would be to pass the result of "for" to "dorun". If your primary goal is to get the sequence of names, continue to use "for" and avoid the "println", but understand that unless you do something with the result, it won't actually be produced. A way to "force" all items to be evaluated is to pass the result of "for" to "doall". In either case, you'll avoid the confusing mixture of output that gets printed by the code you posted. --Steve --~--~---------~--~----~------------~-------~--~----~ 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 To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
