You could do something like this, which is just a generalization of group-by to the multiple value case (except that group-by actually uses transients):
user> (defn groups-by [f coll] (reduce (fn [acc x] (let [ks (f x)] (reduce (fn [acc' k] (update-in acc' [k] #(conj (or % []) x))) acc ks))) {} coll)) #'user/groups-by user> (groups-by #(range 1 (inc %)) [1 2 3]) {3 [3], 2 [2 3], 1 [1 2 3]} (This isn't the return value you say you want, but it seems to be the right return value, unless I've misunderstood the problem: 1, 2, and 3 all include 1, but only 3 includes 3.) You can define regular group-by in terms of this function as (defn group-by [f coll] (groups-by (comp vector f) coll)). On Mon, Jul 8, 2013 at 12:25 PM, Colin Yates <colin.ya...@gmail.com> wrote: > Hi, > > I have a sequence of items and want to group them into categories, the > value of which is a function of the item. This sounds exactly what > group-by is after. > > The kicker is that the function could return multiple values. Imagine > each item was a date range and I wanted to group them by the number of days > in that date range. > > For example, (group-by #(range 1 (inc %)) [1 2 3] => {(1) [1] (1 2) [2] (1 > 2 3) [3]}. I want {1 [1] 2 [1 2] 3 [1 2 3]}. > > Any ideas? > > Thanks! > > Col > > -- > -- > 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/groups/opt_out. > > > -- Ben Wolfson "Human kind has used its intelligence to vary the flavour of drinks, which may be sweet, aromatic, fermented or spirit-based. ... Family and social life also offer numerous other occasions to consume drinks for pleasure." [Larousse, "Drink" entry] -- -- 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/groups/opt_out.