Re: [boost] Formal review request for Hash2

Ivan Matek wrote:

Thank you for the answers.

On Tue, Dec 3, 2024 at 1:54 AM Peter Dimov mailto:pdimov@gmail.com > wrote:

Either way, N3980 is what I liked best, so that's what I based the library on.

Regarding design: I noticed all hash_append* functions take flavor so users often have to write {} argument .

Do you think there would be some benefit for easy use helper, e.g. to have something like this from example boost::hash2::fnv1a_32 h1; int v1[4] = { 1, 2, 3, 4 }; boost::hash2::hash_append( h1, {}, v1 ); writable also as

boost::hash2::simple_hash h1; int v1[4] = { 1, 2, 3, 4 }; h1.append( h1, v1 ); // shorter fn name, no {}, simple_hash flavor is always default flavor

I don't think the {} is a burden, because you generally only write it once or twice at top level. In the tag_invoke methods you need to pass the flavor downstream. Providing an easy way to omit the flavor also encourages the mistake of forgetting to pass it. I don't see anything particularly wrong with the simple_hash adaptor, but I also don't think it will save that much typing either. If you find yourself invoking hash_append with {} repeatedly, something is probably not right. The examples in the documentation that do it are illustrative, real code doesn't need to do that. E.g. you never do this boost::hash2::hash_append( h2, {}, get<0>(v1) ); boost::hash2::hash_append( h2, {}, get<1>(v1) ); boost::hash2::hash_append( h2, {}, get<2>(v1) ); You just invoke hash_append once, with v1. And you never do this boost::hash2::hash_append( h, {}, v.x ); boost::hash2::hash_append( h, {}, v.y ); boost::hash2::hash_append( h, {}, v.z ); You do this instead boost::hash2::hash_append( h, f, v.x ); boost::hash2::hash_append( h, f, v.y ); boost::hash2::hash_append( h, f, v.z ); where f is your flavor argument.