The idea is to gradually, over a few steps, move from a Java implementation to a pure Clojure implementation. A this step the Clojure implementation is called by the Java JUnit-test (see complete test below). In the last step, the Java-references will be removed from the Clojure implementation and the JUnit test replaced by Clojure tests.
The complete code, including Java, Groovy and current Clojure implementation and a micro-benchmark, can be found here: http://code.google.com/p/pnehm-java-to-cool-language-x/source/browse The complete JUnit test: public class OrdererTestUsingJava extends TestCase { 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); unordered = Arrays.asList("b", "d", "d", "e", "b", "a", "c", "a"); ordered = orderer.orderByFreq(unordered); assertEquals(Arrays.asList("a", "b", "d", "c", "e"), ordered); unordered = new ArrayList<String>(); ordered = orderer.orderByFreq(unordered); assertTrue(unordered.isEmpty()); assertTrue(ordered.isEmpty()); } public void testJavaImpl() { doTestOrderByFreq(new JavaOrderer()); } public void testClojureImpl() { doTestOrderByFreq(new step3.pnehm.ClojureOrderer()); } public void testGroovyImpl() { doTestOrderByFreq(new GroovyOrderer()); } } /Patrik On Thu, Jul 9, 2009 at 3:23 PM, Sean Devlin<francoisdev...@gmail.com> wrote: > > 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 > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
