fix: make non-uniform rebinning work for Weight() and friends

[Saransh-cpp]

Fixes #971

Uses View's addition when adding the views during non-uniform rebinning.

[matthewfeickert]

cc @andrzejnovak

[andrzejnovak]

Works (and propagates to hist!). Thanks a lot!

[matthewfeickert]

@Saransh-cpp I'll let you merge in the event there's any final small things you wanted to get in here.

[Saransh-cpp]

Thanks! I don't have merge/write access to boost-histogram. Please feel free to merge :)

[matthewfeickert]

Ah okay I'll also ask @henryiii for review and merge then.

[henryiii]

Are all the fields addable? That is, for every type, can you just directly add the fields? For example, for the Mean storage, this is the definition of __iadd__:

boost-histogram/include/bh_python/accumulators/mean.hpp

Lines 61 to 77 in df21e44

	mean& operator+=(const mean& rhs) noexcept {
	if(rhs.count == 0)
	return *this;
	const auto mu1 = value;
	const auto mu2 = rhs.value;
	const auto n1 = count;
	const auto n2 = rhs.count;
	count += rhs.count;
	value = (n1 * mu1 + n2 * mu2) / count;
	_sum_of_deltas_squared += rhs._sum_of_deltas_squared;
	_sum_of_deltas_squared
	+= n1 * (value - mu1) * (value - mu1) + n2 * (value - mu2) * (value - mu2);
	return *this;
	}

I think we can just use this, though, by exposing it via a ufunc. I'm looking at this soon, but got distracted updating and fixing things in #973.

[henryiii]

Fixed. Thanks!

[matthewfeickert]

Thanks @henryiii and @Saransh-cpp!

Would it be possible to get a patch release with this out?

[henryiii]

1.5.1 is out. :)