(concat sequence [val]) would often be preferable to
(conj (into [] sequence) val) because the former solution maintains laziness. On Tue, Feb 18, 2014 at 9:28 PM, Laurent Droin <laurentdr...@gmail.com>wrote: > Ah, thank you. "interleave" is what I was looking for. I looked for > "weave", "zip", "map", "concat", and all the "see also" but did not find > "interleave". > Interleave will of course not handle the last value in the categories > collection so my first instinct will be to call (into [] ) on the map > returned by interleave, and to add (using conj) the (last categories) to > the vector. Not sure whether there is a better way. > > > On Tuesday, February 18, 2014 9:17:54 PM UTC-8, Michael Gardner wrote: > >> You may be interested in the core function 'interleave'. As for (into >> []), it's perfectly idiomatic as long as you actually need to return a >> vector and not just some kind of sequence (the more common case). But note >> also the mapv/filterv/reduce-kv family of functions, though they're not >> directly applicable here. >> >> On Feb 18, 2014, at 22:58 , Laurent Droin <lauren...@gmail.com> wrote: >> >> > Hi, >> > >> > Continuing my little pet project (small program really) to learn >> Clojure, I am now working on a function whose description would be >> something like: >> > "Returns a collection 'weaving' 2 collections (boundaries into >> categories). >> > Boundaries must have one element less than categories. >> > For example, if categories is [:z1 :z2 :z3 :z4 :z5] >> > and boundaries is [120 150 165 180] >> > returns [:z1 120 :z2 150 :z3 165 :z4 180 :z5]" >> > >> > Assume the precondition is enforced. >> > If categories has n elements, boundaries has n-1. >> > >> > I have tried to come up with a good implementation. I actually came up >> with two, one that is non recursive, and one that is recursive. But I'm not >> fully satisfied. I have the feeling that it's possible to make the function >> simpler, and more elegant but I only know a subset of Clojure and am surely >> missing some good idioms that I could/should be using. >> > So once again, relying on feedback from experienced Clojurists to show >> me the way :-) >> > >> > Here is what I have so far: >> > >> > 1- the non recursive function - based on mapcat >> > (defn build-quantize-defs >> > >> > >> > [categories boundaries] >> > >> > >> > (conj (into [] (mapcat #(vector %1 %2) categories boundaries)) (last >> categories))) >> > >> > 2 - the recursive function >> > (defn build-quantize-defs-recur [categories boundaries] >> > >> > >> > (let [c (first categories) b (first boundaries)] >> > >> > >> > (if (nil? b) >> > >> > >> > [c] >> > >> > >> > (into [] (concat [c] [b] (build-quantize-defs-recur (rest categories) >> (rest boundaries))))))) >> > >> > Both functions work (on my example at least). >> > >> > One of the things I don't like, is my abusing (or the feeling that I am >> abusing anyway) of this "into [] " idiom. I find myself constantly turning >> things into vectors. That doesn't seem right and maybe I am using it in >> places it's not needed. That's probably because I don't quite have a very >> good idea of how collections work just yet. >> > >> > Thanks for any feedback. >> > -- > 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/groups/opt_out. > -- 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/groups/opt_out.
