I didn't expect my question would initiate such a wonderful discussion, I'm speechless. Thank you all guys, you are amazing. Alex, your posts killed in a very good way :) It was really helpful to morph the code and transform it.
On Dec 6, 11:14 am, Ken Wesson <kwess...@gmail.com> wrote: > On Mon, Dec 6, 2010 at 4:02 AM, nickik <nick...@gmail.com> wrote: > > The easy (and good) solution is to pass the running result onlong the > > way. This can be done in diffrent ways. > > > First the CL Style where you creat a new function in you function that > > then does all the work. (from > > Ken Wesson) > > > (defn list-length [coll] > > (let [ll (fn [n s] > > (if s > > (recur (inc n) (next s)) > > n))] > > (ll 0 (seq coll)))) > > > I don't really like this because the core logic is somwhat hidden. > > ??? > > > Then we could use arity functions. (Alex Osborne) > > > (defn list-length > > ([coll] (list-length coll 0)) > > ([coll n] (if-let [s (seq coll)] > > (recur (rest s) (inc n)) > > n))) > > > This is nice style in my opinion > > Not in mine -- it exposes a public API of > list-length-plus-some-integer that a) doesn't make much sense and b) > is unlikely to be supported, since the implementation could be changed > to one that doesn't expose this. Of course sometimes a user wants to > add something to a length of a seq and then they could get a slight > speedup by using (list-length s n) instead of (+ n (list-length s)), > but that is c) premature optimization in the typical case. > > > > > > > but I would do it like this: > > > (defn list-lenght [coll] > > (loop [coll coll n 0] > > (if (empty? coll) > > n > > (recur (rest coll) (inc n))))) > > > or with seq instead of empty? > > > (defn list-lenght [coll] > > (loop [coll coll n 0] > > (if (seq coll) > > (recur (rest coll) (inc n)) > > n))) > > > Hope that helps a little. > > Why not > > (defn list-length [coll] > (let [s (seq coll)] > (loop [s s n 0] > (if s > (recur (next s) (inc n)) > n)))) > > ? This may be slightly more efficient at no cost in clarity. -- 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
