Each arity defined for a particular Clojure function is actually a separate "method" under the hood for that particular functional instance. `recur` in Clojure should be thought of as more like a primitive looping construct than a recursive call to some named function.
The documentation for the recur special form explains this in more detail: http://clojure.org/reference/special_forms#recur. On Monday, April 18, 2016 at 4:16:30 PM UTC-4, andmed wrote: > > Hello > > I am just a beginner Clojure programmer and I am unhappy with the way > recur behaves in Clojure > > I have implemented kata from here > https://github.com/alvarogarcia7/kata-formulation-find-comments/pull/3 > What it does: it outputs 'comments' (sequences starting with "#" or "//") > and ignores 'comments' in quotes > > Here is the code: > > (def comment-s '("#" "//")) > (def quote-s '("'" "\"")) > > (defn comment-s? [s] > (filter #(.startsWith s %) comment-s)) > > (defn quote-s? [s] > (filter #(.startsWith s %) quote-s)) > > (defn find-comment-in-line > "We implement a FSM via an overloaded function -- when inside a quote, > pass two arguments, including opening quote symb, otherwise just one > (string itself). Don't know yet hot to recur in an > ([s] (when (pos? (count s)) > (if-let [cs (seq (comment-s? s))] > (subs s (count (first cs))) ; yes, a comment symbol found, just > return the remainder of a string > (if-let [qs (seq (quote-s? s))] ; no, lets check for an opening > quote > (find-comment-in-line (subs s 1) qs) ; yes, an opening quote > found, now go look for an end quote > (find-comment-in-line (subs s 1)))))) ; no, just some other > symbol found, check for the rest > ([s q] (when (pos? (count s)) > (if-let [qs (seq (quote-s? s))] ; lets check if it is a quote > (if (= qs q) ; is it a closing quote? > (find-comment-in-line (subs s 1)) ; yes, lets check for the rest > (find-comment-in-line (subs s 1) q)))))) ; no, just ignore the > symbol, continue looking for a closing quote > > My idea was to make it via recur: it does not work however because recur > apparently binds to an implementation with particular number of arguments, > not to a function call, and I can not see any reason why it would not. > > With recur I was getting > Caused by: java.lang.IllegalArgumentException: Mismatched argument count > to recur, expected: 1 args, got: 2 > > > I guess the code is a bit "imperative" and imperative programmer I am. > Also, I can make recur work with a nullable argument and a helper function, > still... is there any reason Clojure can not bind recur to a function call > in accordance with the number of arguments passed? > > -- 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.
