Thanks to both of you, this looks more like what I am used to with clojure. The transpose function is the trick here :-)
Best Regards, Sven Am Freitag, 15. Mai 2015 10:35:11 UTC+2 schrieb Ray Miller: > > If I've understood the problem correctly, you can simplify the code by > implementing a transpose function: > > (defn transpose [xs] (apply map vector xs)) > > Then define a wanted? function for filtering the lines you want to > include: > > (defn wanted? [xs] (some zero? xs)) > > ...and a helper function to left-pad a vector with zeroes: > > (defn lpad [n xs] (vec (concat (repeat (- n (count xs)) 0) xs))) > > So your main function would look something like: > > (defn process [xs] (let [n (count (first xs))] (vec (map (partial lpad > n) (transpose (filter wanted? (transpose xs))))))) > > On 15 May 2015 at 09:01, Sven Richter <sve...@googlemail.com <javascript:>> > wrote: > > HI, > > > > I just posted a question to stackoverflows code review > > page: > http://codereview.stackexchange.com/questions/90809/remove-lines-from-a-2d-vec-in-clojure > > > > > As there is not much traffic regarding clojure I also double post to > this > > list in the hope to get some good answers. You might respond here or > there, > > whatever you like best. > > > > I have some code here that I am very unhappy with. The task I am trying > to > > accomplish is this. > > > > Given a 2d vec like this: > > > > [[0 2 0] [1 3 5] [3 3 0]] > > which can contain positive ints including zero I want to remove all > _lines_ > > that are greater zero. > > Whereas the definition of _line_ is the following: > > A _line_ is represented by the position n in every vec inside the 2d > vec. So > > my example above has three lines: > > > > [0 1 3], [2 3 3] and [0 5 0]. > > > > The line that I want to remove from it according to my algortihm is **[2 > 3 > > 3]** because every element is greater than zero. > > > > So my 2d vec would now look like this: > > > > [[0 0] [1 5] [3 0]] > > > > And finally I want to pad the vecs to their original size filling them > with > > zero for every removed line, so that it looks finally like this: > > > > [[0 0 0] [0 1 5] [0 3 0]] > > > > This is what I came up with: > > > > (defn in? > > "true if seq contains elm" > > [seq elm] > > (some #(= elm %) seq)) > > > > (defn not-in? > > "true if seq does not contain elm" > > [seq elm] > > (not (in? seq elm))) > > > > (defn all-greater-zero-at > > "Given a 2-d vec [[0 1] [0 2]] return true if all elements at 'at' > are > > greater than zero" > > [v at] > > (not-in? (map #(if (> (nth % at) 0) true false) v) false)) > > > > (defn to-be-removed > > "Returns a seq of positions to be removed (0 3 4)" > > [v width] > > (reduce (fn [a b] (if (all-greater-zero-at v b) (conj a b) a)) [] > > (range width))) > > > > (defn remove-at > > "Removes an element from a 1d vec" > > [v at] > > (into [] (concat (subvec v 0 at) (subvec v (+ at 1) (count v))))) > > > > (defn insert-at > > "inserts an element into a 1d vec" > > [v elm at] > > (into [] (concat (subvec v 0 at) elm (subvec v at (count v))))) > > > > (defn remove-and-replace-all-at > > [v at] > > (map #(insert-at (remove-at % at) [0] at) v)) > > > > (defn replace-full-by-zero [v width] > > (reduce (fn [a b] (remove-and-replace-all-at a b)) v > (to-be-removed v > > width))) > > > > (defn remove-zeros [v at] > > (reduce (fn [a b] (conj a (remove-at b at))) [] v)) > > > > (defn fill-with-zeros > > "Takes a 2d vec and pads ith with zeros up to width" > > [v width] > > (map #(into [] (concat (take (- width (count (first v))) (repeat > 0)) > > %)) v)) > > > > (defn clean-grid > > "removes all full lines" > > [fbz tbr] > > (loop [acc fbz tbr tbr i 0] > > (if (empty? tbr) > > acc > > (recur (remove-zeros acc (- (first tbr) i)) (rest tbr) (inc > i))))) > > > > (defn remove-full-lines [v width] > > (let [fbz (replace-full-by-zero v width) > > tbr (to-be-removed v width) > > cleaned-grid (clean-grid fbz tbr)] > > (into [] (fill-with-zeros cleaned-grid width)))) > > > > This seems like a lot of code for such a "simple" algorithm and I assume > > there are a lot of better ways to do that, but just did not come up with > a > > better one, so, please, go ahead and fix it, if you want to :-) > > > > Best Regards, > > Sven > > > > -- > > You received this message because you are subscribed to the Google > > Groups "Clojure" group. > > To post to this group, send email to clo...@googlegroups.com > <javascript:> > > Note that posts from new members are moderated - please be patient with > your > > first post. > > To unsubscribe from this group, send email to > > clojure+u...@googlegroups.com <javascript:> > > 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+u...@googlegroups.com <javascript:>. > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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