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4566. The element_type definition of scaled_accessor and conjugated_accessor are not quite right

Section: 29.9.8.2 [linalg.scaled.scaledaccessor], 29.9.9.2 [linalg.conj.conjugatedaccessor] Status: New Submitter: Hewill Kang Opened: 2026-04-08 Last modified: 2026-04-11

Priority: Not Prioritized

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Discussion:

The scaled_accessor defines element_type as const decltype(declval<ScalingFactor>() * ...), but its access returns (scaling_factor() * ...), where scaling_factor() returns const ScalingFactor&.

Furthermore, both scaled_accessor and conjugated_accessor's access construct NestedAccessor::element_type via nested-accessor.access(p, i), but this may not be well-formed.

Proposed resolution:

This wording is relative to N5032.

1. Modify 29.9.8.2 [linalg.scaled.scaledaccessor] as indicated:

   namespace std::linalg {
     template<class ScalingFactor, class NestedAccessor>
     class scaled_accessor {
     public:
       using element_type =
         const decltype(declval<const ScalingFactor&>() * 
                        typename declval<NestedAccessor::element_type>(
                           declval<typename NestedAccessor::reference>()));
       […]
     };
   }
   

2. Modify 29.9.9.2 [linalg.conj.conjugatedaccessor] as indicated:

   namespace std::linalg {
     template<class NestedAccessor>
     class scaled_accessor {
     public:
       using element_type =
         const decltype(conj-if-needed(
                          typename declval<NestedAccessor::element_type>(
                            declval<typename NestedAccessor::reference>())));
       […]
     };
   }