On Fri, Dec 26, 2008 at 10:43 PM, Mark Volkmann <r.mark.volkm...@gmail.com> wrote: > > Why does > > (for [x (range 3)] (println x)) > > output > > (0 > nil 1 > nil 2 > nil) > > when run in the REPL instead of > > 0 > 1 > 2
This is because println returns nil every time it's run. user=> (println "test") test nil user=> Also: user=> (for [x (range 3)] nil) (nil nil nil) user=> So the result of the for is a seq containing three nils. The output from println is interspersed with the printing of the seq. > and nothing at all when run from a script? It doesn't print anything when run from a script because range returns a lazy sequence. Here's a recent post with a similar question: http://groups.google.com/group/clojure/browse_thread/thread/53a32d222c3b40e3# Chouser said the following: > > This does not work - prints nothing - why?: > > (defn pretty-print-row [row] > > (map print row)) > > Because 'map' is lazy, and won't evaluate 'print' on any of the items > sequence unless necessary. For functions with side-effects (like > 'print') you'll generally need 'doseq', loop/recur, or 'dorun'. -- Michael Wood <esiot...@gmail.com> --~--~---------~--~----~------------~-------~--~----~ 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 clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
