Re: Formal review request for Hash2

From: Peter Dimov (pdimov_at_[hidden])
Date: 2024-12-03 13:25:28

Alexander Grund wrote:
> Am 03.12.24 um 12:47 schrieb Ivan Matek via Boost:
> >> 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 );
> >
> > Yes, but then again I am passing f multiple times. I don't want it to
> > sound like I am making a big deal out of this, I can just do something
> > like(and I actually use this idiom a lot) const auto append = [&]
> > (const auto& val){hash_append (h, f, val);} and use that "partially
> > applied" helper, in case I actually need to do hash_append multiple
> > times.
> I think there is space for such a helper:
>      boost::hash2::hasher append(h, f); // Or ...::hasher append(h) for default
> flavor
>      append(v.x);
>      append(v.y);
>      append(v.z);
> 
> As the equivalent for the above sequence. Basically make your lambda
> available as a named type.
> That might make it easier given that the flavor at the 2nd cannot be defaulted.

I already said this, but let's do it again: the flavor can't be defaulted on purpose,
because you shouldn't be defaulting it, as it's a mistake to do so.

You need to use the flavor passed as an argument, not the default one.