1 files changed, 10 insertions, 0 deletions
diff --git a/impl/IdSet.hpp b/impl/IdSet.hpp
index 99f89cc..950b1e1 100644
--- a/impl/IdSet.hpp
+++ b/impl/IdSet.hpp
@@ -39,6 +39,16 @@ class IdSet {
     }
   }
 
+  IdSet inverse() const {
+    IdSet other(_range);
+    for (unsigned int i = 0; i < _range; ++i) {
+      if (_set.find(i) == _set.end()) {
+        other._set.insert(i);
+      }
+    }
+    return other;
+  }
+
   bool contains(const T& obj) const {
     return _set.find(obj.id()) != _set.end();
   }