ncomp would be faster if it's implemented a la exponentiation by squaring. On Mon, Nov 16, 2015 at 12:55 PM, Ben Wolfson <wolf...@gmail.com> wrote:
> If you rearrange the arguments of your proposed three-argument iterate: > > (defn iterate > ... > ([f n x] > (if (zero? n) > x > (recur f (f x) (dec n)))) > > it supports partial application of the multiply-composed function to > different arguments more easily, which suggests redefinition as: > > (defn ncomp [f n] > (loop [g identity n n] > (if (zero? n) > g > (recur (comp g f) (dec n))))) > > This seems to come closer to matching what's desired from the > three-argument iterate without confusingly (as you note) overloading > "iterate": you want f applied n times to x and the stream of intermediate > values isn't really of interest. > > On Mon, Nov 16, 2015 at 12:37 PM, Jason Felice <jason.m.fel...@gmail.com> > wrote: > >> >> I *frequently* see: >> >> (nth (iterate foo bar) n) >> >> And: >> >> (->> (iterate foo bar) >> (drop n) >> first) >> >> I've also coded this in `avi` after being surprised no such thing exists: >> >> (defn n-times >> [thing n a-fn] >> (reduce >> (fn [thing n] >> (a-fn thing)) >> thing >> (range n))) >> >> (which is kind of a bad implementation, now that I think of it): >> >> Would it be useful to file a ticket for a new arity for iterate?: >> >> (defn iterate >> ... >> ([f x n] >> (if (zero? n) >> x >> (recur f (f x) (dec n)))) >> >> There's a little bit of weirdness - this returns a single value, while >> the other arity returns a lazy sequence. However, I think it's the correct >> name (and the original arity might have better been named "iterations" for >> symmetry with "reduce" and "reductions"). But ah well. >> >> Thoughts? >> >> -- >> 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. >> > > > > -- > Ben Wolfson > "Human kind has used its intelligence to vary the flavour of drinks, which > may be sweet, aromatic, fermented or spirit-based. ... Family and social > life also offer numerous other occasions to consume drinks for pleasure." > [Larousse, "Drink" entry] > > -- Ben Wolfson "Human kind has used its intelligence to vary the flavour of drinks, which may be sweet, aromatic, fermented or spirit-based. ... Family and social life also offer numerous other occasions to consume drinks for pleasure." [Larousse, "Drink" entry] -- 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.
