sampler.hh: Implement access to items

src/graph/generation/sampler.hh

@@ -96,6 +96,26 @@ public:
     size_t size() const { return _items.size(); }
     bool empty() const { return _items.empty(); }
 
+    const Value& operator[](size_t i) const
+    {
+        return _items[i];
+    }
+
+    const auto& items() const
+    {
+        return _items;
+    }
+
+    const auto begin() const
+    {
+        return _items.begin();
+    }
+
+    const auto end() const
+    {
+        return _items.end();
+    }
+
 private:
 
     typedef typename mpl::if_<KeepReference,