1 files changed, 67 insertions, 0 deletions

diff --git a/subprojects/logic/src/main/java/tools/refinery/logic/term/ConstantTerm.java b/subprojects/logic/src/main/java/tools/refinery/logic/term/ConstantTerm.java
new file mode 100644
index 00000000..69c7e5f6
--- /dev/null
+++ b/subprojects/logic/src/main/java/tools/refinery/logic/term/ConstantTerm.java
@@ -0,0 +1,67 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.logic.term;
+
+import tools.refinery.logic.equality.LiteralHashCodeHelper;
+import tools.refinery.logic.InvalidQueryException;
+import tools.refinery.logic.equality.LiteralEqualityHelper;
+import tools.refinery.logic.substitution.Substitution;
+import tools.refinery.logic.valuation.Valuation;
+
+import java.util.Objects;
+import java.util.Set;
+
+// {@link Object#equals(Object)} is implemented by {@link AbstractTerm}.
+@SuppressWarnings("squid:S2160")
+public final class ConstantTerm<T> extends AbstractTerm<T> {
+        private final T value;
+
+        public ConstantTerm(Class<T> type, T value) {
+                super(type);
+                if (value != null && !type.isInstance(value)) {
+                        throw new InvalidQueryException("Value %s is not an instance of %s".formatted(value, type.getName()));
+                }
+                this.value = value;
+        }
+
+        public T getValue() {
+                return value;
+        }
+
+        @Override
+        public T evaluate(Valuation valuation) {
+                return getValue();
+        }
+
+        @Override
+        public Term<T> substitute(Substitution substitution) {
+                return this;
+        }
+
+        @Override
+        public boolean equalsWithSubstitution(LiteralEqualityHelper helper, AnyTerm other) {
+                if (!super.equalsWithSubstitution(helper, other)) {
+                        return false;
+                }
+                var otherConstantTerm = (ConstantTerm<?>) other;
+                return Objects.equals(value, otherConstantTerm.value);
+        }
+
+        @Override
+        public int hashCodeWithSubstitution(LiteralHashCodeHelper helper) {
+                return Objects.hash(super.hashCodeWithSubstitution(helper), Objects.hash(value));
+        }
+
+        @Override
+        public Set<AnyDataVariable> getInputVariables() {
+                return Set.of();
+        }
+
+        @Override
+        public String toString() {
+                return value.toString();
+        }
+}