All customization points pertaining to buffer sequences should be removed

[pdimov]

We should remove all tag_invoke customization points pertaining to buffer sequences, and all custom buffer sequence types that only exist because they customize an operation. Buffer sequences should be generic ranges of const_bufffer or mutable_buffer (or more precisely, any generic range should be accepted as a buffer sequence; const_buffer and mutable_buffer by itself would still be able to serve as buffer sequences.)

[vinniefalco]

What does this refer to?

all custom buffer sequence types that only exist because they customize an operation"

[pdimov]

buffer_array, buffer_pair...

[vinniefalco]

buffer_pair is an alias for std::array

buffer_array has some features that we would lose:

• Union-based storage, no default construction of unused slots
• Filters empty buffers during construction
• Cached size_ for O(1) total byte count
• Two construction modes: silent truncation vs std::length_error
• Implicit conversion to std::span<value_type>
• Constructs from any matching buffer sequence, single buffer, or iterator range

[pdimov]

Everything has features. The question is whether those features belong in Capy, and by extension, in the std proposal for the fundamental operations.

[vinniefalco]

Yes of course, I am just showing the tradeoffs. buffer_array can be an implementation detail / QoL. And we can always add it later, if there is evidence of need.