fix FunctionTermImpl#equals s.t. also subtypes can be equal

alpha-commons/src/main/java/at/ac/tuwien/kr/alpha/commons/rules/heads/ActionHeadImpl.java

@@ -9,6 +9,7 @@
 import at.ac.tuwien.kr.alpha.api.rules.heads.ActionHead;
 import at.ac.tuwien.kr.alpha.api.terms.Term;
 import at.ac.tuwien.kr.alpha.api.terms.VariableTerm;
+import org.apache.commons.lang3.StringUtils;
 
 class ActionHeadImpl implements ActionHead {
 
@@ -55,4 +56,8 @@ public VariableTerm getActionOutputTerm() {
 		return actionOutputTerm;
 	}
 
+	public String toString() {
+		return atom.toString() + " : @" + actionName + "(" + StringUtils.join(actionInputTerms, ", ") + ") = " + actionOutputTerm;
+	}
+
 }

alpha-commons/src/main/java/at/ac/tuwien/kr/alpha/commons/terms/FunctionTermImpl.java

@@ -98,16 +98,19 @@ public boolean equals(Object o) {
 		if (this == o) {
 			return true;
 		}
-		if (o == null || getClass() != o.getClass()) {
+		if (o == null) {
+			return false;
+		}
+		if (!(o instanceof FunctionTerm)) {
 			return false;
 		}
 
-		FunctionTermImpl that = (FunctionTermImpl) o;
+		FunctionTerm that = (FunctionTerm) o;
 
-		if (!symbol.equals(that.symbol)) {
+		if (!symbol.equals(that.getSymbol())) {
 			return false;
 		}
-		return terms.equals(that.terms);
+		return terms.equals(that.getTerms());
 	}
 
 	@Override
@@ -121,24 +124,24 @@ public int compareTo(Term o) {
 			return 0;
 		}
 
-		if (!(o instanceof FunctionTermImpl)) {
+		if (!(o instanceof FunctionTerm)) {
 			return super.compareTo(o);
 		}
 
-		FunctionTermImpl other = (FunctionTermImpl) o;
+		FunctionTerm other = (FunctionTerm) o;
 
-		if (terms.size() != other.terms.size()) {
-			return terms.size() - other.terms.size();
+		if (terms.size() != other.getTerms().size()) {
+			return terms.size() - other.getTerms().size();
 		}
 
-		int result = symbol.compareTo(other.symbol);
+		int result = symbol.compareTo(other.getSymbol());
 
 		if (result != 0) {
 			return result;
 		}
 
 		for (int i = 0; i < terms.size(); i++) {
-			result = terms.get(i).compareTo(other.terms.get(i));
+			result = terms.get(i).compareTo(other.getTerms().get(i));
 			if (result != 0) {
 				return result;
 			}

alpha-commons/src/test/java/at/ac/tuwien/kr/alpha/commons/terms/TermsTest.java

@@ -4,6 +4,7 @@
 
 import java.util.List;
 
+import at.ac.tuwien.kr.alpha.api.terms.FunctionTerm;
 import org.junit.jupiter.api.Test;
 
 import at.ac.tuwien.kr.alpha.api.terms.ConstantTerm;
@@ -30,4 +31,15 @@ public void stringsAsTermList() {
 		assertEquals("\"blubb\"", terms.get(1).toString());
 	}
 
+	/**
+	 * Reproduction test for an error observed while testing evolog actions.
+	 */
+	@Test
+	public void functionTermVsActionSuccessTermHash() {
+		FunctionTerm funcTerm = Terms.newFunctionTerm("success", Terms.newFunctionTerm("stream", Terms.newConstant("outputStream_2")));
+		FunctionTerm actionSuccessTerm = Terms.actionSuccess(Terms.newFunctionTerm("stream", Terms.newConstant("outputStream_2")));
+		assertEquals(funcTerm, actionSuccessTerm);
+		assertEquals(funcTerm.hashCode(), actionSuccessTerm.hashCode());
+	}
+
 }

alpha-core/src/main/java/at/ac/tuwien/kr/alpha/core/grounder/IndexedInstanceStorage.java

@@ -112,7 +112,8 @@ public void removeIndexPosition(int position) {
 	 * @return true if the instance is already contained in the storage.
 	 */
 	public boolean containsInstance(Instance instance) {
-		return instances.contains(instance);
+		boolean contains = instances.contains(instance);
+		return contains; // TODO remove extra variable, debugging only
 	}
 
 	public void addInstance(Instance instance) {