Push in FVariadicParticleContainer with position and missing attributes

The last attributes may be ommited when pushing in
FVariadicParticleContainer. The last commits broke that behaviour.

Src/Adaptive/FVariadicParticleContainer.hpp

@@ -40,7 +40,8 @@ struct FVariadicParticleContainerBase {
  * \tparam Allocator The allocator to use
  *
  * The Particle type must define an `as_tuple` method that returns a tuple
- * representation of the particle. It is expected in general to follow the form:
+ * representation of the particle. It is expected to hold position values before
+ * attribute values.
  *
  * ~~~
  * posX, posY, poZ, attributes...
@@ -118,8 +119,30 @@ public:
      */
     template<typename Position, typename... Args>
     void push(const Position& position, Args... args) {
-        Particle temp_part{position, args...};
-        this->push(temp_part.as_tuple());
+        using vt = typename FBase::value_type;
+
+        constexpr auto Dim = Particle::position_t::Dim;
+        constexpr int vt_size = std::tuple_size<vt>::value;
+        constexpr int missing_offset = Dim + sizeof...(args);
+        constexpr int missing_size = vt_size - missing_offset;
+
+        this->push_impl(
+            inria::make_index_sequence<Dim>{},
+            inria::make_index_sequence<missing_size>{},
+            position, args...);
+    }
+
+    template<typename Position, typename... Args, std::size_t... Is, std::size_t... Js, typename... Ts>
+    void push_impl(inria::index_sequence<Is...>,
+                   inria::index_sequence<Js...>,
+                   const Position& position,
+                   Args... args) {
+        using vt = typename FBase::value_type;
+        constexpr auto Dim = Particle::position_t::Dim;
+        constexpr int missing_offset = Dim + sizeof...(args);
+
+        this->push_back(std::get<Is>(position)..., args...,
+                        std::tuple_element_t<missing_offset + Js, vt>{}...);
     }
 
     /**