clojure map-keys

Someone in #clojure was asking about how to case-insensitively check the keys of a map. The best answer anyone present at the time came up with was pre-processing the map by naming, lowering, and keywordifying the keywords. We then found out the asker was looking for keys in nested maps, so I wrote a function for that.

After writing the function I realized I could extract the lowering function and let it take a function to apply to all keys of m and all keys in m's vals.

Here is the map-keys function with the lower-key function extracted. I run it on some goofy data at the end. Try it in a REPL.

	(defn lower-key [x]
	(if (or (string? x) (keyword? x))
	(-> x name .toLowerCase keyword)
	x))
	(defn map-keys
	"applies f to each key of m. also to keys of m's vals and so on."
	[f m]
	(zipmap
	(map (fn [k]
	(f k))
	(keys m))
	(map (fn [v]
	(if (map? v)
	(map-keys f v)
	v))
	(vals m))))
	(map-keys lower-key
	{:aBaB 123
	"CAsasas" {1 "doesn't apply to non-string non-keyword keys"
	:yoGURt "mmMMm"
	:notVALUES "either"}})

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