Don't forget destructuring: (for [[a b c] signal] (map (partial reduce +) [a b c]))
and, ((fn [[[a b c][d e f]]] (map (partial reduce +) [a b c d e f])) signal) While messing around with that, I was wondering if there were some function that allowed you to destructure on-demand. Like, => (destruct [[[a b c][d e f]]] signal) (1 2 3 4) (2 3 4 5) (3 4 5 6) (3 4 5 6) (4 5 6 7) (5 6 7 8) Anything like that exist? -- John On Wed, Aug 25, 2010 at 10:36 AM, James Reeves <jree...@weavejester.com> wrote: > I think you're getting confused. > > (map reduce + %) won't work, because the signature of the map function > is (map func & colls). In other words, the second argument is expected > to be a collection, but you've put in +, which is a function. > > When dealing with nested collections, you may want to work from the > inside out. So take one of your inner lists: > > s1: (1 2 3 4) > > (reduce + s1) => 10 > (apply + s1) => 10 > > You can use reduce or apply to sum the lists. On the next level, we have: > > s2: ((1 2 3 4) (2 3 4 5) (3 4 5 6)) > > (map (partial reduce +) s2) => (10 14 18) > > So we're using map to sum each list. (partial reduce +) is just > another way of writing #(reduce + %). > > Next is the final layer: > > signal: (((1 2 3 4) (2 3 4 5) (3 4 5 6)) ((3 4 5 6) (4 5 6 7) (5 6 7 8))) > > (map (partial map (partial reduce +)) signal) > => ((10 14 18) (18 22 26)) > > Again, we add a map, and use partial. We could perhaps make this a > little clearer by using for: > > (for [s signal] > (for [c s] (reduce + c))) > > - James > > > On 25 August 2010 15:06, Glen Rubin <rubing...@gmail.com> wrote: >> After toying around at the REPL I realize that I have been working >> with a heretofore invalid understanding of collections. For example, >> working with the following collection(s): >> >> signal: >> (((1 2 3 4) (2 3 4 5) (3 4 5 6)) ((3 4 5 6) (4 5 6 7) (5 6 7 8))) >> >> I wanted to sum each individual list: e.g. (1 2 3 4) = (10) >> >> I thought I could do this as follows: >> >> (map #(map reduce + %) signal) >> >> This resulted in an error, so trying to comprehend why I ran the >> following: >> >> (map #(map identity (take 1 %)) signal) >> >> which results in, >> (((1 2 3 4)) ((3 4 5 6))) >> >> So, clojure sees 'signal' as 2 collections, whereas I thought it was a >> single collection. This makes me concerned that I have been doing >> everything wrong thus far and getting computational errors. :( So, >> how should I sum each individual list in the above collections? >> >> -- >> 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 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 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
