write_cbor_iterative and write_msgpack_iterative (and their *_value_or_push helpers) were identical but for the head, scalar, and key writers. They are now one template over a small policy struct, so everything inlines. BON8 keeps its own walker (open string run, closing marker), noted in a comment. Signed-off-by: Niels Lohmann <mail@nlohmann.me>