Alexander Grund wrote:
If the hash-algorithms would accept `span<const void>` (or <const char>) instead as the only `update` method (no need for overloads) we could have
hash_append( span{v} ); hash_append( span{st} );
by accepting a templated span and casting it to the span-type expected by the hash-algorithms. And/or a `hash2::span` that accepts any range-like in the ctor and doing the cast.
Yes, obviously. However, there's an additional concern here that people perhaps don't appreciate. The hash algorithm requirements govern user-defined algorithms as well. N3980 wasn't supposed to be a library of hash algorithms; it was supposed to be a framework into which any user-defined hash algorithm can plug into, and be used for hashing C++ objects. That's why the hash algorithm interface is kept minimal and uncomplicated (which is at odds with making it as ergonomic as possible.) I can obviously support any form of `update` by making it templated and do the appropriate enable_if incantations, but I don't want to impose this requirement on hash algorithm authors. And I don't want to force hash algorithm authors to have to include <boost/hash2/span.hpp>, because this would mean a physical dependency on Hash2. At the moment, you can define a hash algorithm without including anything from Hash2, or anything from Boost. And that's how it has to be.