Gorgeous! Thanks, Moe! (Chris says hi back :)) > On Aug 19, 2015, at 7:51 PM, Moe Aboulkheir <m...@nervous.io> wrote: > > Laurens, > > I don't think I've encountered an identical function I can point you to, but > here's an alternative implementation: > > (defn partition-when [pred coll] > (lazy-seq > (when-let [[h & t] (seq coll)] > (let [[run remains] (split-with (complement pred) t)] > (cons (cons h run) (partition-when pred remains)))))) > > Do you like that any better? > > P.S: Say Hi to Chris for me! > > Take care, > Moe > > > On Thu, Aug 20, 2015 at 1:34 AM, Laurens Van Houtven <_...@lvh.io > <mailto:_...@lvh.io>> wrote: > Hi, > > > I needed a function that partitions (coll a) => (coll (coll a)), starting a > new subcoll whenever a given pred is true. Use case: I have a sequence of > rows; these rows form groups; I want to group them. A group is started by a > header; so I want a new coll whenever my is-header? pred returns true. > > I found an implementation that used partition-by on the mailing list, but > this had some issues: if multiple elems next to each other were true under > the pred, it wouldn’t create a new pred for each one. > > I came up with the following implementation. > > (defn ^:private partition-when > "Partitions the coll whenever (f elem) is true." > [pred coll] > (-> (reduce (fn [[first & rest :as groups] elem] > (if (pred elem) > (conj groups [elem]) > (conj rest (conj first elem)))) > '() > coll) > reverse)) > > It feels like this could be written a *lot* better. With Haskell’s > Data.List.Split, this becomes: > > partitionWith p xs = filter (/= []) (split (whenElt p) xs) > > (thanks to my colleague Christopher Armstrong for the help with the Haskell > version) > > It would *almost* be partitionWith p = split (whenElt p), but for some reason > split sometimes returns empty lists. Granted, this is a specialized library; > I’d be more than happy to get partition-when from a 3rd party. It’d be even > nicer if it was in Clojure though :) > > > thanks > lvh > > -- > 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 > <mailto: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 > <mailto:clojure%2bunsubscr...@googlegroups.com> > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > <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 > <mailto:clojure+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > > > -- > 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 > <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 > <mailto:clojure+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>.
-- 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.
