P1673R12: Varna 2023 LWG review comments

[mhoemmen]

Varna 2023 LWG review comments

2023/06/14

"your matrix_layout_policy isn’t a layout_policy because the latter needs to support any extent" -- not clear whether this is an action item.

2023/06/15

Change to mdspan's specification, not to P1673?

A possible problematic interpretation of [mdspan.layout.policy.reqmts]. Suggested edit: A type MP meets the layout mapping policy requirements if for a type E that is a specialization of extents such that MP::mapping<E> is valid, MP::mapping<E> denotes a type X that meets the layout mapping requirements ([mdspan.layout.reqmts]), and for which the qualified-id X::layout_type is valid and denotes the type MP and the qualified-id X::extents_type denotes E.

TODO list

• Remove reference to P2642R2. P1673 is orthogonal to P2642.
• Change the exposition-only is-mdspan to be a variable template.
• Change "it will do so in read-only fashion" to "it does so ...."
• Implement changes in P1673R12: LWG comments from chat #390
  • Fix in-vector (and analogous exposition-only concepts) declaration
  • Fix "xT"
  • Figure out what wording LWG wants for abs, conj, imag, and real