One question on design intent before feedback. Is your intent to have
this Clojure code called by Java code later?
On Jul 9, 7:31 am, Patrik Fredriksson <patri...@gmail.com> wrote:
> Hi!
>
> I started to look closer at Clojure after Rich Hickey's presentation
> at QCon London in March, this is my first post. I spend my days
> programming Java, but my journey as developer did actually start with
> an ML programming course many years ago. It has been great fun to
> re-discover the functional style of programming again! This list is a
> great source of knowledge.
>
> A colleague of mine wrote an article about how to convert a piece of
> Java code to Groovy a few months ago. As an exercise I thought I
> should do the same, but to Clojure of course. I'd really appreciate
> some feedback on the solution. I hope you aren't too sick of these
> kind of posts just yet :-)
>
> The code orders a list of characters, first by frequency and then
> alphabetically if two characters happen to have the same frequency.
>
> A Java unit test:
>
> private void doTestOrderByFreq(Orderer orderer) {
> List<String> unordered = Arrays.asList("b", "d", "b", "b",
> "a", "c", "a");
> List<String> ordered = orderer.orderByFreq(unordered);
> assertEquals(Arrays.asList("b", "a", "c", "d"), ordered);
>
> }
>
> A Java implementation:
>
> public class JavaOrderer implements Orderer {
>
> public List<String> orderByFreq(List<String> in) {
> final Bag bag = new HashBag(in);
> List<String> out = new ArrayList<String>(bag.uniqueSet());
>
> Collections.sort(out, new Comparator<String>() {
> public int compare(String a, String b) {
> int freq = Integer.valueOf(
> bag.getCount(b)).compareTo(bag.getCount(a)
> );
> return freq != 0 ? freq : a.compareTo(b);
> }
> });
>
> return out;
> }
>
> }
>
> My shot at a Clojure implementation, with inspiration from a previous
> post in this group on a similar problem:
>
> (ns step3.pnehm.clojure-orderer
> (:gen-class
> :name step3.pnehm.ClojureOrderer
> :implements [pnehm.Orderer]
> ))
>
> (defn count-words [coll]
> (reduce #(merge-with + %1 {%2 1}) {} coll))
>
> (defn cmpr [[val1 freq1] [val2 freq2]]
> (let [freq (compare freq2 freq1)]
> (if (not= freq 0) freq (compare val1 val2))))
>
> (defn -orderByFreq [_ coll]
> (if (empty? coll) () (keys (sort cmpr (count-words coll)))))
>
> Orderer is a simple Java interface making it easy to call different
> implementations from the JUnit test:
>
> List<String> orderByFreq(List<String> in);
>
> All kinds of feedback are welcome, both on style and the chosen solution.
>
> Many thanks!
>
> /Patrik
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