1 files changed, 21 insertions, 0 deletions

diff --git a/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/CheckEvaluator.java b/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/CheckEvaluator.java
new file mode 100644
index 00000000..ada154d4
--- /dev/null
+++ b/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/CheckEvaluator.java
@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.store.query.viatra.internal.pquery;
+
+import tools.refinery.viatra.runtime.matchers.psystem.IValueProvider;
+import tools.refinery.store.query.term.Term;
+
+class CheckEvaluator extends TermEvaluator<Boolean> {
+        public CheckEvaluator(Term<Boolean> term) {
+                super(term);
+        }
+
+        @Override
+        public Object evaluateExpression(IValueProvider provider) {
+                var result = super.evaluateExpression(provider);
+                return result == null ? Boolean.FALSE : result;
+        }
+}