sclass PointSetSimilarity { Set set1, set2; int totalPoints; int sharedPoints; *(Set *set1, Set *set2) { for (Pt p : set1) { ++totalPoints; if (set2.contains(p)) ++sharedPoints; } for (Pt p : set2) if (!set1.contains(p)) ++totalPoints; } double get() { ret doubleRatio(sharedPoints, totalPoints); } }