clojure sort always return a list

Question

To sort a vector in clojure

(sort [ 2 3 1 4])

returns a list (sorted)

(1 2 3 4)

I can turn it back into the vector by

(into [] (sort [ 2 3 1 4]))

which is kind of inconvenient.

But if I sort a map/dictionary in clojure

(sort {2 "" 3 "" 1 "" 4 ""})

the return

([1 ""] [2 ""] [3 ""] [4 ""])

How do I turn it back into a sorted map? Or is there a better sort function that keeps the type/shape of the input?

not a dupe, but stackoverflow.com/q/1989301/599075 indicates that there isn't a great way — Andbdrew
– Andbdrew, Commented Feb 18, 2016 at 23:02
I was about to post an answer involving empty and into, but it turned out to be much less useful than I expected. — Sam Estep
– Sam Estep, Commented Feb 18, 2016 at 23:11
Perhaps something like (apply into ((juxt empty sort) coll)), doesn't seem very useful though. — glts
– glts, Commented Feb 18, 2016 at 23:23
btw, sort doesn't return a list, but an ArraySeq. (class (sort [2 3 1 4])) ;=> clojure.lang.ArraySeq, vs (class '(4 3 2 1)) ;=> clojure.lang.PersistentList. Clojure has lots of different collection data structures, but there are only a few collection delimiter characters available, so there are things that aren't lists but whose printed representations use parentheses. There are not many functions that return lists, I believe. list is an exception. :-) — Mars
– Mars, Commented Feb 19, 2016 at 5:09

Shlomi · Accepted Answer · 2016-02-19 00:52:10Z

3

I dont know of a general way to always keep the original type/shape.

In case of a sorted map, its important to know that a regular map in clojure has no order (at least nothing you can or should rely on). For that clojure has sorted-map. There is also a useful function sorted-map-by that allows you to specify your own ordering.

So, in your example:

(into (sorted-map)  {2 "" 3 "" 1 "" 4 ""})
;; {1 "", 2 "", 3 "", 4 ""}

edited Feb 19, 2016 at 0:52

answered Feb 19, 2016 at 0:43

Shlomi

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