This is a solved problem. The trick is to use a higher-higher order function...
http://fulldisclojure.blogspot.com/2010/01/12-fn-proposal-same-multisame.html On Dec 7, 7:38 am, Daniel Janus <nath...@gmail.com> wrote: > While on the topic, I'd like to raise a naming issue. > > The 'mapmap' function seems to be a recurring theme (see, > e.g.,http://tech.puredanger.com/2010/09/24/meet-my-little-friend-mapmap/) > and many Clojure projects include one -- Incanter comes to mind. My > project used to, too. But we found out that the name "mapmap" has its > deficiencies. > > First, it conflates the two senses of the word "map" (1. noun -- an > object implementing IPersistentMap; 2. verb -- to apply a function to > each element of a collection, producing a new one) by putting them > right next to each other. This impairs code readability: I once found > myself typing (mapmap #(map ... ) ...) -- it's unobvious at first > sight which "map" is used in which sense. > > Second, all these implementations of mapmap floating around are > mutually incompatible, which partly stems from the fact that it is > unclear from the name what the argument of mapmap should be. Should it > be a value->value function? Or should it take two arguments, a key and > a value? Or should it take a [key value] pair? > > Actually, each one of these flavors is useful on different occasions. > So to differentiate between them, we've now dropped mapmap and use > transform-v and transform-kv instead. Here they are, with docstrings: > > (defn transform-kv > "Transforms each entry in a map with f and returns the resulting > map. > f should take and return a key/value pair. Similar to > clojure.contrib.generic.functor/fmap, but can take keys into account. > Works on any seq of pairs (not necessarily maps), always returning > maps." > [f x] > (into {} (map (fn [[k v]] (f k v)) x))) > > (defn transform-v > "Like transform-kv, but takes a value->value function, leaving keys > intact." > [f x] > (into {} (map (fn [[k v]] [k (f v)]) x))) -- 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
