How is fluokitten's fold any better than using seqs like (map f a b) would? Both create intermediate collections.
On Fri, Sep 23, 2016 at 11:40 AM, Dragan Djuric <draga...@gmail.com> wrote: > If you do not insist on vanilla clojure, but can use a library, fold from > fluokitten might enable you to do this. It is similar to reduce, but > accepts multiple arguments. Give it a vararg folding function that prints > what you need and ignores the first parameter, and you'd get what you asked > for. > > > On Friday, September 23, 2016 at 7:15:42 PM UTC+2, Mars0i wrote: >> >> On Friday, September 23, 2016 at 11:11:07 AM UTC-5, Alan Thompson wrote: >>> >>> Huh. I was also unaware of the run! function. >>> >>> I suppose you could always write it like this: >>> >>> (def x (vec (range 3))) >>> (def y (vec (reverse x))) >>> >>> (run! >>> (fn [[x y]] (println x y)) >>> >>> (map vector x y)) >>> >>> >>> > lein run >>> 0 2 >>> 1 1 >>> 2 0 >>> >>> >> Yes. But that's got the same problem. Doesn't matter with a toy >> example, but the (map vector ...) could be undesirable with large >> collections in performance-critical code. >> >> although the plain old for loop with dotimes looks simpler: >>> >>> (dotimes [i (count x) ] >>> (println (x i) (y i))) >>> >>> >>> maybe that is the best answer? It is hard to beat the flexibility of a a >>> loop and an explicit index. >>> >> >> I agree that this is clearer, but it kind of bothers me to index through >> a vector sequentially in Clojure. We need indexing In Clojure because >> sometimes you need to access a vector more arbitrarily. If you're just >> walking the vector in order, we have better methods--as long as we don't >> want to walk multiple vectors in the same order for side effects. >> >> However, the real drawback of the dotimes method is that it's not >> efficient for the general case; it could be slow on lists, lazy sequences, >> etc. (again, on non-toy examples). Many of the most convenient Clojure >> functions return lazy sequences. Even the non-lazy sequences returned by >> transducers aren't efficiently indexable, afaik. Of course you can always >> throw any sequence into 'vec' and get out a vector, but that's an >> unnecessary transformation if you just want to iterate through the >> sequences element by element. >> >> If I'm writing a function that will plot points or that will write data >> to a file, it shouldn't be a requirement for the sake of efficiency that >> the data come in the form of vectors. I should be able to pass in the data >> in whatever form is easiest. Right now, if I wanted efficiency for walking >> through sequences in the same order, without creating unnecessary data >> structures, I'd have to write the function using loop/recur. On the other >> hand, if I wanted the cross product of the sequences, I'd use doseq and be >> done a lot quicker with clearer code. >> > -- > 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/d/optout. > -- “One of the main causes of the fall of the Roman Empire was that–lacking zero–they had no way to indicate successful termination of their C programs.” (Robert Firth) -- 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/d/optout.
