I think you've explained it well. You can use https://clojure.github.io/clojure/clojure.core-api.html#clojure.core/completing to patch in a better completion arity for - (here I think identity is what you want and that is the default for completing):
(transduce xf (completing -) 0 (range 10)) On Monday, January 25, 2016 at 7:12:42 AM UTC-6, Mark Tinsley wrote: > > Hi all, > > Could I have some clarification on something, I know how to solve the > issue I just want to make sure I understand the reasons behind it, given > the following: > > (def xf > (comp > (filter odd?) > (map inc) > (take 5))) > > > (transduce xf + 0 (range 10)) > > I get the answer: => 30 > > Makes sense, now if I do this: > > (transduce xf - 0 (range 10)) > > I get the answer.... => 30 > > But... > > (reduce - 0 (eduction xf (range 10))) > > gives => -30 > > I can see why this is, looking at > https://github.com/clojure/clojure/blob/010864f8ed828f8d261807b7345f1a539c5b20df/src/clj/clojure/core.clj#L6587 > > the binding ret in the let has the reduced value. This is then passed to > the reducers arity-1 function, which preforms something equivalent to the > following (- -30) to give 30. > > The reason for the arity-1 function is to complete/cleanup state as seen > in the partition-all function > https://github.com/clojure/clojure/blob/010864f8ed828f8d261807b7345f1a539c5b20df/src/clj/clojure/core.clj#L6954 > > As '-' historically had an arity-1 function we cannot update the > behaviour, this may well be the case for other functions. > > Am I right in the above or am I missing something? > > Thanks, > > Mark > > > -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
