I've seen situations where #_ still affects the code (or at least allows it to compile).
reduce expects a function with 2 parameters, one for If you try to use the #() macro, but only use the first implicit parameter (%1), it'll blow up with an IllegalArgumentException: user=> (reduce #(+ %1 1) 0 [1 2 3 5 8]) java.lang.IllegalArgumentException: Wrong number of args passed to: user$eval--87$fn (NO_SOURCE_FILE:0) If you add in #_ %2, and it will succeed as the compiler then knows that it's a 2 argument function: user=> (reduce #(+ 1 %1 #_ %2) 0 [1 2 6 4 4]) 5 (though, really, the intent is clearer if you just define the function with explicit args) user=> (reduce (fn [i n] (+ i 1)) 0 [1 2 3 5 8]) 5 There might be other situations though where #_ and the thing it "comments" can still have an impact on how the code executes, just something I ran across recently that slightly adjusted my thinking on #_. -Ted On Tue, Aug 3, 2010 at 2:35 PM, Meikel Brandmeyer <m...@kotka.de> wrote: > Hi, > > Am 03.08.2010 um 16:45 schrieb Yang Dong: > > > I've read the src of core.clj of Clojure 1.1.0. Originally I thought > > the meaning of #_ is to comment the thing after it, sort of like `;'. > > But the in the src of core.clj in 1.2.0-RC1. The definition of reduce > > is overrided to use the internal-reduce function. The defn line, is > > preceded by `#_'. But in 1.1.0, it's not preceded by this reader > > macro. So, I'm confused... > > You are absolutely right. The #_ is kind of comment. And in fact the > override with the internal reduce function is commented out (ie. it’s not > active) in 1.2. > > Sincerely > Meikel > > -- > 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<clojure%2bunsubscr...@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 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
