add begin(), end() to util::stack_vector

src/util/stack_vector.hpp

@@ -94,6 +94,22 @@ namespace util {
         bool full() const {
             return size_ == capacity;
         }
+
+        auto begin() {
+            return data_;
+        }
+
+        auto end() {
+            return data_ + size_;
+        }
+
+        auto begin() const {
+            return data_;
+        }
+
+        auto end() const {
+            return data_ + size_;
+        }
     private:
         T data_[capacity];
         int size_;