Get particle selection from WeightedRelationTable

• Add temporary code to use to get a selection of particles from a filtered Relation Table, useful in this case as pointed by @roneil.

Phys/RelatedInfoTools/src/WeightedRelationTable.cpp

@@ -22,9 +22,10 @@
 
 namespace {
   using WeightedRelationTable = LHCb::Relation1D<LHCb::Particle, LHCb::Particle>;
-  using Transformer =
+  using RelTableTransformer =
       LHCb::Algorithm::Transformer<WeightedRelationTable( const LHCb::Particle::Range&, const LHCb::Particle::Range& )>;
-  using weight_t = bool;
+  using SelectionTransformer = LHCb::Algorithm::Transformer<LHCb::Particle::Selection( const WeightedRelationTable& )>;
+  using weight_t             = bool;
 
   struct Funct {
     constexpr static auto PropertyName = "Cut";
@@ -60,14 +61,14 @@ namespace {
 
 // This algorithm includes GetPhotonsForDalitzDecay
 
-struct WeightedRelTableAlg : with_functors<Transformer, Funct> {
+struct WeightedRelTableAlg final : with_functors<RelTableTransformer, Funct> {
   // ==========================================================================
   /** the standard constructor
    *  @param name algorithm instance name
    *  @param pSvc service locator
    */
   WeightedRelTableAlg( const std::string& name, ISvcLocator* pSvc )
-      : with_functors<Transformer, Funct>::with_functors(
+      : with_functors<RelTableTransformer, Funct>::with_functors(
             name, pSvc, {KeyValue{"InputCandidates", ""}, KeyValue{"ReferenceParticles", ""}},
             KeyValue{"OutputRelations", ""} ) {}
 
@@ -102,4 +103,22 @@ private:
   mutable Gaudi::Accumulators::SummingCounter<> m_outCount{this, "#OutputParticles"};
 };
 
+struct SelectionFromWeightedRelationTable final : SelectionTransformer {
+  // ==========================================================================
+  /** the standard constructor
+   *  @param name algorithm instance name
+   *  @param pSvc service locator
+   */
+
+  SelectionFromWeightedRelationTable( const std::string& name, ISvcLocator* svcLoc )
+      : Transformer( name, svcLoc, KeyValue( "InputRelations", "" ), KeyValue( "OutputLocation", "" ) ) {}
+
+  LHCb::Particle::Selection operator()( const WeightedRelationTable& input ) const override {
+    LHCb::Particle::Selection selection;
+    for ( const auto& rel : input.relations() ) selection.push_back( rel.to() );
+    return selection;
+  }
+};
+
 DECLARE_COMPONENT( WeightedRelTableAlg )
+DECLARE_COMPONENT( SelectionFromWeightedRelationTable )