| 1 | package uk.co.zonetora.fj.util; |
| 2 | |
| 3 | import java.util.ArrayList; |
| 4 | import java.util.Iterator; |
| 5 | import java.util.List; |
| 6 | |
| 7 | import static java.lang.Math.*; |
| 8 | |
| 9 | public class ListUtil { |
| 10 | |
| 11 | public static <X,Y> List<X> mapFst(List<Tuple<X,Y>> list) { |
| 12 | List<X> outList = new ArrayList<X>(); |
| 13 | |
| 14 | for(Tuple<X,?> t : list) { |
| 15 | outList.add(t.getX()); |
| 16 | } |
| 17 | |
| 18 | return outList; |
| 19 | |
| 20 | } |
| 21 | |
| 22 | public static <X,Y> List<Y> mapSnd(List<Tuple<X,Y>> list) { |
| 23 | List<Y> outList = new ArrayList<Y>(); |
| 24 | |
| 25 | for(Tuple<?,Y> t : list) { |
| 26 | outList.add(t.getY()); |
| 27 | } |
| 28 | |
| 29 | return outList; |
| 30 | } |
| 31 | |
| 32 | public static <X,Y> List<Tuple<X,Y>> zip(List<X> xs, List<Y> ys) { |
| 33 | Iterator<X> xi = xs.iterator(); |
| 34 | Iterator<Y> yi = ys.iterator(); |
| 35 | |
| 36 | List<Tuple<X,Y>> out = new ArrayList<Tuple<X,Y>>(min(xs.size(), ys.size())); |
| 37 | |
| 38 | while(xi.hasNext()) { |
| 39 | if(yi.hasNext()) { |
| 40 | out.add(new Tuple<X,Y>(xi.next(), yi.next())); |
| 41 | continue; |
| 42 | } |
| 43 | break; |
| 44 | } |
| 45 | |
| 46 | return out; |
| 47 | } |
| 48 | } |