Cleanup struct Entities

Signed-off-by: yamacir-kit <httperror@404-notfound.jp>

docs/developer_guide/OpenSCENARIOSupport.md

@@ -55,7 +55,7 @@ The OpenSCENARIO XML standard [does not define](https://releases.asam.net/OpenSC
 
 ### Command
 
-OpenSCENARIO XML standard states that `CustomCommandAction` can be used to either issue a command to the simulation environment or start an external script. 
+OpenSCENARIO XML standard states that `CustomCommandAction` can be used to either issue a command to the simulation environment or start an external script.
 
 For OpenSCENARIO interpreters implemented in scripting languages such as Python, this action is often implemented as a call to an external script file written in the same language as the host language. However, `scenario_simulator_v2` is implemented in C++ and we cannot simply implement such a feature. Therefore, `scenario_simulator_v2` treats the string given in `CustomCommandAction.type` as a command and executes it on a subprocess, as `sh` does.
 
@@ -308,7 +308,7 @@ Currently, the only way to know the result of the simulation is by viewing the s
 | DynamicsDimension                            | 1.3               |                                            |
 | DynamicsShape                                | 1.3 (partial)     | [detail](#DynamicsShape)                   |
 | EndOfRoadCondition                           | unimplemented     |                                            |
-| Entities                                     | 1.3 (partial)     | [detail](#Entities)                        |
+| Entities                                     | 1.3.1             |                                            |
 | EntityAction                                 | 1.3               |                                            |
 | EntityCondition                              | 1.3 (partial)     | [detail](#EntityCondition)                 |
 | EntityDistribution                           | unimplemented     |                                            |
@@ -637,10 +637,6 @@ Currently, the only way to know the result of the simulation is by viewing the s
 
 - Enumeration literal `sinusoidal` is **not** supported.
 
-#### Entities
-
-- Property `EntitySelection` is **not** supported.
-
 #### EntityCondition
 
 - Properties `EndOfRoadCondition`, `OffroadCondition`, `TimeToCollisionCondition`, `RelativeDistanceCondition`, `TraveledDistanceCondition`, `AngleCondition`, and `RelativeAngleCondition` are **not** supported.

openscenario/openscenario_interpreter/include/openscenario_interpreter/syntax/entities.hpp

@@ -24,18 +24,25 @@ namespace openscenario_interpreter
 {
 inline namespace syntax
 {
-/* ---- Entities ---------------------------------------------------------------
- *
- *  <xsd:complexType name="Entities">
- *    <xsd:sequence>
- *      <xsd:element name="ScenarioObject" minOccurs="0" maxOccurs="unbounded" type="ScenarioObject"/>
- *      <xsd:element name="EntitySelection" minOccurs="0" maxOccurs="unbounded" type="EntitySelection"/>
- *    </xsd:sequence>
- *  </xsd:complexType>
- *
- * -------------------------------------------------------------------------- */
-struct Entities : public std::unordered_map<std::string, Object>  // TODO to be data member
+/*
+   Entities (OpenSCENARIO XML 1.3.1)
+
+   Definition of entities (scenario objects or entity selections) in
+   a scenario.
+
+   <xsd:complexType name="Entities">
+     <xsd:sequence>
+       <xsd:element name="ScenarioObject" type="ScenarioObject" minOccurs="0" maxOccurs="unbounded"/>
+       <xsd:element name="EntitySelection" type="EntitySelection" minOccurs="0" maxOccurs="unbounded"/>
+     </xsd:sequence>
+   </xsd:complexType>
+*/
+struct Entities : private std::unordered_map<std::string, Object>
 {
+  using std::unordered_map<std::string, Object>::at;
+  using std::unordered_map<std::string, Object>::begin;
+  using std::unordered_map<std::string, Object>::end;
+
   explicit Entities(const pugi::xml_node &, Scope &);
 
   auto isAdded(const Entity &) const -> bool;