Think in terms of numbering the possible split locations: a b c 1 2
So the possible partitions are represented by [1], [2], [1 2], i.e., all the non-empty subsets of [1 2]. So write a function that goes from this numbering scheme to partitions (e.g., using subvec) and use combinatorics' subsets function. On Wed, Mar 15, 2017 at 8:35 PM, Paul Gowder <paul.gow...@gmail.com> wrote: > Hi everyone, > > Does anyone know of a straightforward way to get something like > clojure.math/combinatorics/partitions that works more like partition in > the core library, that is, that only selects partitions with adjacent > elements? > > In other words, right now this is the problem: > > (require '[clojure.math.combinatorics :as c]) > (c/partitions [:a :b :c] :min 2) > > => (([:a :b] [:c]) ([:a :c] [:b]) ([:a] [:b :c]) ([:a] [:b] [:c])) > > But that ([:a :c] [:b]) there in the second position isn't a proper > partition because :a and :c aren't adjacent in the original vector. > > I feel like there's got to be a standard, canonical solution for this, or > some existing sequence or combinatorics function with a funny name that > just returns (([a :b] [:c]) ([:a] [:b :c]) ([:a] [:b] [:c])) in this > situation. I just don't know it... > > The best I can come up with is kind of a hackish workaround that only > works when the original vector is sorted, namely, flattening all the > partitions and testing to see whether they are sorted too, i.e.: > > (require '[clojure.math.combinatorics :as c]) > > (defn test-fn [part] > (let [f (flatten part)] > (= f (sort f)))) > > (filter test-fn (c/partitions [:a :b :c] :min 2)) > > => (([:a :b] [:c]) ([:a] [:b :c]) ([:a] [:b] [:c])) ; Yay! :-) > > And that works, but, as noted, only when the original vector is sorted. > What if someone wanted to preserve adjacencies in an unsorted vector? > > All thoughts appreciated, thanks! > > Cheers, > > -Paul > > -- > 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. > -- 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.
