DFT: no error for optional json arguments

src/storm-dft/parser/DFTJsonParser.cpp

@@ -34,16 +34,18 @@ namespace storm {
 
         template<typename ValueType>
         storm::storage::DFT<ValueType> DFTJsonParser<ValueType>::parseJson(json const& jsonInput) {
-            // Parse parameters
+            // Try to parse parameters
+            if (jsonInput.find("parameters") != jsonInput.end()) {
                 json parameters = jsonInput.at("parameters");
+                STORM_LOG_THROW(parameters.empty() || (std::is_same<ValueType, storm::RationalFunction>::value), storm::exceptions::NotSupportedException, "Parameters only allowed when using rational functions.");
                 for (auto it = parameters.begin(); it != parameters.end(); ++it) {
-            STORM_LOG_THROW((std::is_same<ValueType, storm::RationalFunction>::value), storm::exceptions::NotSupportedException, "Parameters only allowed when using rational functions.");
                     std::string parameter = it.key();
                     storm::expressions::Variable var = manager->declareRationalVariable(parameter);
                     identifierMapping.emplace(var.getName(), var);
                     parser.setIdentifierMapping(identifierMapping);
                     STORM_LOG_TRACE("Added parameter: " << var.getName());
                 }
+            }
 
             json nodes = jsonInput.at("nodes");
             // Start by building mapping from ids to their unique names
@@ -102,6 +104,8 @@ namespace storm {
                     success = false;
                 }
 
+                // Try to set layout information
+                if (element.find("position") != element.end()) {
                     // Do not set layout for dependencies
                     // This does not work because dependencies might be splitted
                     // TODO: do splitting later in rewriting step
@@ -112,6 +116,7 @@ namespace storm {
                         double y = position.at("y");
                         builder.addLayoutInfo(name, x / 7, y / 7);
                     }
+                }
                 STORM_LOG_THROW(success, storm::exceptions::FileIoException, "Error while adding element '" << element << "'.");
             }