Fasta builders.

pkg/fasta/lib/src/combinator.dart

Index: pkg/fasta/lib/src/combinator.dart
diff --git a/pkg/fasta/lib/src/combinator.dart b/pkg/fasta/lib/src/combinator.dart
new file mode 100644
index 0000000000000000000000000000000000000000..b2a5c36f7d383c5d51ca3e05e1e36e2a4814fc62
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+++ b/pkg/fasta/lib/src/combinator.dart
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+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library fasta.combinator;
+
+class Combinator {
+  final bool isShow;
+
+  final Set<String> names;
+
+  Combinator(this.isShow, this.names);
+
+  Combinator.show(Iterable <String> names)
+      : this(true, new Set<String>.from(names));
+
+  Combinator.hide(Iterable <String> names)
+      : this(false, new Set<String>.from(names));
+
+  bool get isHide => !isShow;
+}