Correctly implemented hiding predicates with nested arguments.

tests/TestHiddenPredicateElimination.cpp

@@ -137,4 +137,18 @@ TEST_CASE("[hidden predicate elimination] Hidden predicates are correctly elimin
 		CHECK(output.str() ==
 			"forall V1, V2 (a(V1, V2) <-> exists U1 ((V1 = 1 and V2 = 2 and U1 = 3) or (V1 = 2 and V2 = 4 and U1 = 6)))\n");
 	}
+
+	SECTION("nested arguments are correctly handled when hiding predicates")
+	{
+		input <<
+			"a(X) :- b(c(X)).\n"
+			"b(c(X)) :- c(X).\n"
+			"c(1..4).\n"
+			"#show a/1.";
+		anthem::translate("input", input, context);
+
+		// TODO: simplify further
+		CHECK(output.str() ==
+			"forall V1 (a(V1) <-> exists U1 (c(V1) = c(U1) and U1 in 1..4))\n");
+	}
 }