Wow, I'm impressed. Thanks for the explanation Meikel. Clojure is indeed very expressive.
Another question: I was wondering why there seem to be no macrolet or symbol-macrolet macros in the language. Is it part of the language design or will they be added in future releases? On Nov 20, 10:08 pm, Meikel Brandmeyer <[EMAIL PROTECTED]> wrote: > Hi Rock, > > Am 20.11.2008 um 20:58 schrieb Rock: > > > Peter Seibel's Practical Common Lisp: > > You might want to look at Stuart Halloway's "PCL->Clojure" > series:http://blog.thinkrelevance.com/2008/09/16/pcl-clojure > > > (defmacro with-gensyms [[& names] form] > > `(let ~(apply vector (loop [n names result []] > > (if (nil? n) > > result > > (recur (rest n) > > (conj result (first n) `(gensym)))))) > > ~form)) > > - [[& names]] is actually the same as [names]. The only difference > is that the former will give an error when you don't pass a > collection. > However that, you will get anyway later on... > > - (apply vector ...) can also be done via (vec ...). > > - The loop can also be done with reduce or mapcat. > > (defmacro with-gensyms > [names form] > `(let ~(vec (mapcat (fn [n] [n `(gensym)]) names)) > ~form)) > > or with reduce > > (defmacro with-gensyms > [names form] > `(let ~(vec (reduce #(conj %1 %2 `(gensym)) [] names)) > ~form)) > > or just like that... > > (defmacro with-gensyms > [names form] > `(let ~(vec (interleave names (repeat `(gensym)))) > ~form)) > > So, many ways lead to Rome. :) I think the last one is maybe > the most elegant. > > I think for Clojure, this is not really interesting, because > you have the # notation to create automatic gen-syms on the > fly. This already gets you very far. gensym is only in special > cases necessary. > > (defmacro foo [x] (with-gensyms [xx] `(let [~xx ~x] ~xx))) > vs. > (defmacro foo [x] `(let [x# ~x] x#)) > > Sincerely > Meikel > > smime.p7s > 5KViewDownload --~--~---------~--~----~------------~-------~--~----~ 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 To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
