Index: lib/src/evaluator.dart |
diff --git a/lib/src/evaluator.dart b/lib/src/evaluator.dart |
new file mode 100644 |
index 0000000000000000000000000000000000000000..9102add652703809758b50a3a6d4aa382851639a |
--- /dev/null |
+++ b/lib/src/evaluator.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. |
+ |
+import 'ast.dart'; |
+import 'visitor.dart'; |
+ |
+typedef bool _Semantics(String variable); |
+ |
+/// A visitor for evaluating boolean selectors against a specific set of |
+/// semantics. |
+class Evaluator implements Visitor<bool> { |
+ /// The semantics to evaluate against. |
+ final _Semantics _semantics; |
+ |
+ Evaluator(semantics) |
+ : _semantics = semantics is Iterable |
+ ? semantics.toSet().contains |
+ : semantics; |
+ |
+ bool visitVariable(VariableNode node) => _semantics(node.name); |
+ |
+ bool visitNot(NotNode node) => !node.child.accept(this); |
+ |
+ bool visitOr(OrNode node) => |
+ node.left.accept(this) || node.right.accept(this); |
+ |
+ bool visitAnd(AndNode node) => |
+ node.left.accept(this) && node.right.accept(this); |
+ |
+ bool visitConditional(ConditionalNode node) => node.condition.accept(this) |
+ ? node.whenTrue.accept(this) |
+ : node.whenFalse.accept(this); |
+} |