1 files changed, 74 insertions, 0 deletions

diff --git a/subprojects/logic/src/main/java/tools/refinery/logic/term/UnaryTerm.java b/subprojects/logic/src/main/java/tools/refinery/logic/term/UnaryTerm.java
new file mode 100644
index 00000000..e173de3e
--- /dev/null
+++ b/subprojects/logic/src/main/java/tools/refinery/logic/term/UnaryTerm.java
@@ -0,0 +1,74 @@
+/*
+ * 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.InvalidQueryException;
+import tools.refinery.logic.equality.LiteralEqualityHelper;
+import tools.refinery.logic.equality.LiteralHashCodeHelper;
+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 abstract class UnaryTerm<R, T> extends AbstractTerm<R> {
+        private final Class<T> bodyType;
+        private final Term<T> body;
+
+        protected UnaryTerm(Class<R> type, Class<T> bodyType, Term<T> body) {
+                super(type);
+                if (!body.getType().equals(bodyType)) {
+                        throw new InvalidQueryException("Expected body %s to be of type %s, got %s instead".formatted(body,
+                                        bodyType.getName(), body.getType().getName()));
+                }
+                this.bodyType = bodyType;
+                this.body = body;
+        }
+
+        public Class<T> getBodyType() {
+                return bodyType;
+        }
+
+        public Term<T> getBody() {
+                return body;
+        }
+
+        @Override
+        public R evaluate(Valuation valuation) {
+                var bodyValue = body.evaluate(valuation);
+                return bodyValue == null ? null : doEvaluate(bodyValue);
+        }
+
+        protected abstract R doEvaluate(T bodyValue);
+
+        @Override
+        public boolean equalsWithSubstitution(LiteralEqualityHelper helper, AnyTerm other) {
+                if (!super.equalsWithSubstitution(helper, other)) {
+                        return false;
+                }
+                var otherUnaryTerm = (UnaryTerm<?, ?>) other;
+                return bodyType.equals(otherUnaryTerm.bodyType) && body.equalsWithSubstitution(helper, otherUnaryTerm.body);
+        }
+
+        @Override
+        public int hashCodeWithSubstitution(LiteralHashCodeHelper helper) {
+                return Objects.hash(super.hashCodeWithSubstitution(helper), bodyType, body.hashCodeWithSubstitution(helper));
+        }
+
+        @Override
+        public Term<R> substitute(Substitution substitution) {
+                return doSubstitute(substitution, body.substitute(substitution));
+        }
+
+        protected abstract Term<R> doSubstitute(Substitution substitution, Term<T> substitutedBody);
+
+        @Override
+        public Set<AnyDataVariable> getInputVariables() {
+                return body.getInputVariables();
+        }
+}