2010/11/27 rob levy <r.p.l...@gmail.com> > partition-by does exactly what you need.
Nope. partition-by will split each time the value changes. Not each time a particular value is seen. > > > 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<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
