Vector-as-map destructuring makes sense when you consider that vectors are associative: they map index to value.
(let [{a 1 b 3 :as c} [:a 1 :b 2]] [a b c]) => [1 2 [:a 1 :b 2]] Justin On Tuesday, August 28, 2012 8:30:58 AM UTC-4, Douglas Orr wrote: > > One possibly confusing titbit I came across recently relates to how > Clojure handles destructuring of variable-length argument lists. The > essence is that the destructuring form can appear to influence the 'shape' > of the collection of arguments. Here is what I mean: > > take nothing off the head of the vector, then put all remaining elements > into a vector c: > > user=> (let [[& [:as c]] [:one "one" :two "two"]] (seq c)) > (:one "one" :two "two") > > > take nothing off the head of the vector, then put all remaining elements > into a map c: > > user=> (let [[& {:as c}] [:one "one" :two "two"]] (seq c)) > ([:one "one"] [:two "two"]) > > > Notice how the structure of 'c' has changed due to the destructuring form, > even though in both cases it refers to the whole collection. Digging down > into this a bit, it looks like this depends on the type of the collection > being destructured: > > user=> (let [{:as c} [:one "one" :two "two"]] (seq c)) > (:one "one" :two "two") > > user=> (let [{:as c} (seq [:one "one" :two "two"])] (seq c)) > ([:one "one"] [:two "two"]) > > > I can see why this is necessary for multiple-args destructuring to work, > but I think my small mind finds this 'automatic marshalling' of > lists-or-seqs into maps a bit confusing. Maybe my only real problem is the > destructuring of vectors as maps, which somewhat 'works' in the above > example, but isn't really consistent. Any thoughts? > -- 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