Yeah, it consumes stack just like the Clojurescript version of Iterate. I'm curious if anyone knows how to avoid this. The Clojure version of Iterate is Java; and for some reason 'recur' can't be used inside of lazy-cat (not really documented, but apparently true).
On Tuesday, September 22, 2015 at 9:21:57 PM UTC-7, Max Countryman wrote: > > I wonder if something like this is a little easier to read? > > (defn generate > ([f coll] > (generate f coll (reverse coll))) > ([f coll args] > (let [next-val (apply f args)] > (lazy-cat coll (generate f [next-val] (conj (butlast args) > next-val)))))) > > Where your Fibonacci example becomes: > > (take 100 (generate +’ [1 1])) > > As for your other questions, I can’t be of much help. But isn’t there > nontrivial memory overhead to consider with this approach? > > > On Sep 22, 2015, at 18:19, nchurch <nchu...@gmail.com <javascript:>> > wrote: > > I was going through 4clojure (highly recommended!) and doing the Fibonacci > exercise. It occurred to me that the iterate function could be generalized > in a reasonable way, so that the next value is generated by applying the > function to the last N items so far, where N is the number of initial > arguments beyond the function. Thus: > > (generate inc 1) > > works just like iterate, while > > (generate + 1 1) > > generates the Fibonacci sequence. > > Here's the code: > > (defn generate > [f & more] > (letfn [(recurse > [coll args] > (let [next-val (apply f args)] > (lazy-cat coll (recurse [next-val] (conj (butlast args) > next-val)))))] > (recurse more (reverse more)))) > > > Code is also on Github <https://github.com/nchurch/generate>. > > I see this as part of a larger class of generalized sequence functions: for > instance, extra arguments in a function given to *reduce* could refer to N > arguments back in the sequence (might be useful, for instance, in smoothing a > sequence of values using an average). > > Questions: is there an existing home for this kind of functionality? And > could the above code be improved? (I just used the definition of *iterate* > as a starting point.) > > > > > -- > 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. 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.
