partition-by does exactly what you need. On Sat, Nov 27, 2010 at 3:04 PM, Benny Tsai <benny.t...@gmail.com> wrote:
> Could do it this way. Use index-filter (borrowed from Programming > Clojure) to get the indices where the predicate is true in the > sequence. partition-when-true then just calls subvec with pairs of > indices to get the subsequences. > > coll-end is the index just past the end of the collection. This is > used as a pad element so that the last true index is included in the > pairs, and also accounts for the case where there is only a single > true index. > > (use '[clojure.contrib.seq :only (indexed)]) > > (defn index-filter [pred coll] > (when pred > (for [[idx elt] (indexed coll) :when (pred elt)] idx))) > > (defn partition-when [pred coll] > (let [coll-end (count coll) > indices (index-filter pred coll) > index-pairs (partition 2 1 [coll-end] indices) > coll-vec (vec coll)] > (for [[start end] index-pairs] (subvec coll-vec start end)))) > > user=> (partition-when true? '(true false false true false true true)) > ([true false false] [true false] [true] [true]) > > On Nov 27, 10:02 am, Asim Jalis <asimja...@gmail.com> wrote: > > I want to partition a sequence based on the values of a predicate so > > that every true starts a new sequence in the partition. Here is an > > example of how partition-with could be used: > > > > (partition-when true? '(true false false true false true true)) > > -> '((true false false) (true false) (true) (true)) > > > > I have written this lazy-seq and recursion. However, I was wondering > > if there is a way to do this with core Clojure sequence primitives. > > Any suggestions? > > > > Asim > > -- > > San Francisco, CA > > -- > 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
