1 files changed, 20 insertions, 0 deletions
diff --git a/internal/sets/sets.go b/internal/sets/sets.go
new file mode 100644
index 0000000..f34ae5b
--- /dev/null
+++ b/internal/sets/sets.go
@@ -0,0 +1,20 @@
+// Copyright 2017 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package sets provides sets for storing collections of unique elements.
+package sets
+
+// present is an empty struct used as the "value" in the map[int], since
+// empty structs consume zero bytes (unlike 1 unnecessary byte per bool).
+type present struct{}