Hi Roelof, ClojureDocs.org <http://clojuredocs.org/>is also a great tool for figuring out how to use a specific function. It presents examples created by the community, which are quite helpful when learning the language.
Here's the entry for the assoc <http://clojuredocs.org/clojure.core/assoc> function. Hope it helps, Juan On Wednesday, October 29, 2014 9:53:59 AM UTC-3, Roelof Wobben wrote: > > Thanks all, > > It clear to me that I have to read the explanation or the right wiki page > more carefully. > > I tried all of them and they all give the same answer : > {:title "zbook", :authors [{:name "James"} {:name "Joe"}]} > > Roelof > > > Op woensdag 29 oktober 2014 13:34:32 UTC+1 schreef François Rey: > >> (oops my earlier message isn't quite right, here's the correct one) >> >> You also need to clarify your intention: are you adding an author to a >> list of authors, or setting the single author? >> I suppose the first, but then you need to be clear on what the list of >> authors is. >> In idiomatic clojure you'll want it to be a vector of authors, so if an >> author is a map like {:name "Gerald J. Sussman"}, then :authors must be >> associated to a vector of maps. >> Also bear in mind that assoc is geared towards associative data >> structures such as maps, while conj is geared towards sequential data >> structures such as vectors. >> That being said, you can still use assoc on vectors (indices are the >> keys) and use conj on maps (with a vector in the form of [key value]), but >> that's polymorphism convenience, not idiomatic. >> In the end add to a new author, you need to do: >> (assoc book :authors (conj (get book :authors) new-author)) >> Which can also be made more idiomatic as already mentioned: >> (update-in book [:authors] assoc new-author) >> The twisted way of doing it would be: >> (conj book [:authors (conj (:authors book) new-author)]) >> >> Try this in a REPL: >> >> (def book {:title "zbook" :authors [{:name "James"}]}) >> (def new-author {:name "Joe"}) >> (assoc book :authors (conj (get book :authors) new-author)) >> (update-in book [:authors] conj new-author) >> (conj book [:authors (conj (:authors book) new-author)]) >> >> >> >> >> On 29/10/14 12:20, Roelof Wobben wrote: >> >> Thanks James, >> >> But how do I use assoc with it >> >> I tried this : >> >> (defn add-author [book new-author] >> (assoc book (conj (book :authors) new-author))) >> >> but then I see this message : >> >> >> ArityException Wrong number of args (2) passed to: core$assoc >> clojure.lang.AFn.throwArity (AFn.java:437) >> >> Roelof >> >> >> Op woensdag 29 oktober 2014 12:08:35 UTC+1 schreef James Reeves: >> >>> On 29 October 2014 11:01, Roelof Wobben <rwo...@hotmail.com> wrote: >>>> >>>> For a exercise I have to add something to the end of a existing map. >>>> >>>> So I thought this would work : >>>> >>>> (defn add-author [book new-author] >>>> (assoc book (conj :authors new-author))) >>>> >>> >>> Take a look at that conj expression on its own: >>> >>> (conj :authors new-author) >>> >>> You're trying to conjoin "new-author" onto the keyword :authors, but >>> keywords aren't collections. That's what the error means. It's saying that >>> it expected a collection, but you've supplied a keyword instead. >>> >>> What you want is: >>> >>> (conj (get book :authors) new-author) >>> >>> Which can also be written: >>> >>> (conj (book :authors) new-author) >>> >>> (conj (:authors book) new-author) >>> >>> These two expressions are shortcuts for the above "get" function. They >>> work because maps and keywords can act as functions. >>> >>> - James >>> >> -- >> 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 >> 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 >> 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. >> 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.
