1 files changed, 66 insertions, 0 deletions

diff --git a/subprojects/logic/src/main/java/tools/refinery/logic/term/uppercardinality/UnboundedUpperCardinality.java b/subprojects/logic/src/main/java/tools/refinery/logic/term/uppercardinality/UnboundedUpperCardinality.java
new file mode 100644
index 00000000..b6ecc1bd
--- /dev/null
+++ b/subprojects/logic/src/main/java/tools/refinery/logic/term/uppercardinality/UnboundedUpperCardinality.java
@@ -0,0 +1,66 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.logic.term.uppercardinality;
+
+import org.jetbrains.annotations.NotNull;
+
+// Singleton implementation, because there is only a single countable infinity.
+@SuppressWarnings("squid:S6548")
+public final class UnboundedUpperCardinality implements UpperCardinality {
+        static final UnboundedUpperCardinality INSTANCE = new UnboundedUpperCardinality();
+
+        private UnboundedUpperCardinality() {
+                // Singleton constructor.
+        }
+
+        @Override
+        public UpperCardinality add(UpperCardinality other) {
+                return this;
+        }
+
+        @Override
+        public UpperCardinality take(int count) {
+                return this;
+        }
+
+        @Override
+        public UpperCardinality multiply(UpperCardinality other) {
+                return this;
+        }
+
+        // This should always be greater than any finite cardinality.
+        @SuppressWarnings("ComparatorMethodParameterNotUsed")
+        @Override
+        public int compareTo(@NotNull UpperCardinality upperCardinality) {
+                if (upperCardinality instanceof FiniteUpperCardinality) {
+                        return 1;
+                }
+                if (upperCardinality instanceof UnboundedUpperCardinality) {
+                        return 0;
+                }
+                throw new IllegalArgumentException("Unknown UpperCardinality: " + upperCardinality);
+        }
+
+        @Override
+        public int compareToInt(int value) {
+                return 1;
+        }
+
+        @Override
+        public String toString() {
+                return "*";
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+                return this == obj || (obj != null && getClass() == obj.getClass());
+        }
+
+        @Override
+        public int hashCode() {
+                return -1;
+        }
+}