# Changelog

## Version 1.7

### Version 1.7.1

#### Typing

- Make the `Histogram` type generic, by @henryiii in [#1081][], [#1082][], [#1083][]
- The `MultiCell` storage takes an argument (missed in typing), by @henryiii in [#1080][]

[#1080]: https://github.com/scikit-hep/boost-histogram/pull/1080
[#1081]: https://github.com/scikit-hep/boost-histogram/pull/1081
[#1082]: https://github.com/scikit-hep/boost-histogram/pull/1082
[#1083]: https://github.com/scikit-hep/boost-histogram/pull/1083

### Version 1.7.0

#### Features

- `MultiCell` storage, supporting a variable number of values, by @Superharz in [#1008][]
- Record `growth=True` in writer-info (serialization), and respect it if present by @henryiii in [#1074][]
- Drop Python 3.9 by @henryiii in [#1057][]
- Drop Python 3.13t (use 3.14t instead) by @henryiii in [#1079][]

#### Bug fixes

- Don't add empty metadata dicts by @henryiii in [#1048][]
- Avoid compiler warning: declaration of 'i' hides previous local declaration by @Superharz in [#1068][]

#### Internal

- Refactor `__getitem__` using pattern matching by @henryiii in [#1067][]
- pytest `log_level` is better than `log_cli_level` by @henryiii in [#1059][]
- Setting `__file__` no longer required (pybind11 3.0) by @henryiii in [#1066][]
- This should work on iOS now in cibuildwheel by @henryiii in [#1049][]

[#1008]: https://github.com/scikit-hep/boost-histogram/pull/1008
[#1048]: https://github.com/scikit-hep/boost-histogram/pull/1048
[#1049]: https://github.com/scikit-hep/boost-histogram/pull/1049
[#1057]: https://github.com/scikit-hep/boost-histogram/pull/1057
[#1059]: https://github.com/scikit-hep/boost-histogram/pull/1059
[#1066]: https://github.com/scikit-hep/boost-histogram/pull/1066
[#1067]: https://github.com/scikit-hep/boost-histogram/pull/1067
[#1068]: https://github.com/scikit-hep/boost-histogram/pull/1068
[#1074]: https://github.com/scikit-hep/boost-histogram/pull/1074
[#1079]: https://github.com/scikit-hep/boost-histogram/pull/1079

## Version 1.6

### Version 1.6.1

This release fixes several issues with serialization as it's being prepared
in Hist/uhi.

#### Features

- Support `__dict__` on histogram like axes [#1041][]
- Allow library to be specified in `writer_info` removal [#1042][]

#### Bug fixes

- Avoid mutating lists given in indexing [#1047][]
- Histogram metadata not being serialized correctly [#1038][]
- Unset classic metadata shouldn't show up in serialization [#1039][]
- Set dict correctly when unserializing [#1040][]
- Serialization was broken for N>1D complex storage histograms [#1043][]

[#1038]: https://github.com/scikit-hep/boost-histogram/pull/1038
[#1039]: https://github.com/scikit-hep/boost-histogram/pull/1039
[#1040]: https://github.com/scikit-hep/boost-histogram/pull/1040
[#1041]: https://github.com/scikit-hep/boost-histogram/pull/1041
[#1042]: https://github.com/scikit-hep/boost-histogram/pull/1042
[#1043]: https://github.com/scikit-hep/boost-histogram/pull/1043
[#1047]: https://github.com/scikit-hep/boost-histogram/pull/1047

### Version 1.6.0

This release adds support for UHI serialization for use with the `uhi` library,
supported in the next release of `uhi`. A new diagnostic test has been added
in the wheel, so you can quickly check your compile of boost-histogram without
the full test suite. Quite a few fixes are present, as well, including a fix
for `*=`, setting a range with a scalar, setting with a callable in a slice.
Backend changes include many new clang-tidy checks that reduce the number of
copies and refcount changes. We now build with pybind11 3.0.

This release drops support for Python 3.8, and adds Python 3.14(t), iOS, Windows ARM, and GraalPy.

#### Features

- Initial support for uhi's serialization [#997][], [#1030][], [#1033][], [#1034][], [#1035][]
- Drop Python 3.8 [#976][]
- Support Windows ARM [#1001][]
- Support Python 3.14 and 3.14t [#1018][]
- Support iOS [#1020][], [#1027][]
- Added diagnostics test [#1022][]
- Recommend/use `np.s_` for slicing in dicts [#1002][]

#### Bug fixes

- Support setting ranges with histograms (fixes `*=` too) [#1036][]
- Support a callable in range setting [#1036][]
- Support setting a range with a scalar [#1000][]
- Account for fuzzy edge values in rebinning with edges [#999][]
- Rename C++ metadata to `raw_metadata` [#979][]
- Address lots of clang-tidy suggestions, should be faster with less copies/refcount bumps [#1009][], [#1010][], [#1011][], [#1012][], [#1013][], [#1014][], [#1015][]

#### CI and testing

- Add CMake presets for testing and clang-tidy [#1009][]

[#976]: https://github.com/scikit-hep/boost-histogram/pull/976
[#979]: https://github.com/scikit-hep/boost-histogram/pull/979
[#997]: https://github.com/scikit-hep/boost-histogram/pull/997
[#999]: https://github.com/scikit-hep/boost-histogram/pull/999
[#1000]: https://github.com/scikit-hep/boost-histogram/pull/1000
[#1001]: https://github.com/scikit-hep/boost-histogram/pull/1001

:[#1002]: https://github.com/scikit-hep/boost-histogram/pull/1002
[#1009]: https://github.com/scikit-hep/boost-histogram/pull/1009
[#1010]: https://github.com/scikit-hep/boost-histogram/pull/1010
[#1011]: https://github.com/scikit-hep/boost-histogram/pull/1011
[#1012]: https://github.com/scikit-hep/boost-histogram/pull/1012
[#1013]: https://github.com/scikit-hep/boost-histogram/pull/1013
[#1014]: https://github.com/scikit-hep/boost-histogram/pull/1014
[#1015]: https://github.com/scikit-hep/boost-histogram/pull/1015
[#1018]: https://github.com/scikit-hep/boost-histogram/pull/1018
[#1020]: https://github.com/scikit-hep/boost-histogram/pull/1020
[#1022]: https://github.com/scikit-hep/boost-histogram/pull/1022
[#1027]: https://github.com/scikit-hep/boost-histogram/pull/1027
[#1030]: https://github.com/scikit-hep/boost-histogram/pull/1030
[#1033]: https://github.com/scikit-hep/boost-histogram/pull/1033
[#1034]: https://github.com/scikit-hep/boost-histogram/pull/1034
[#1035]: https://github.com/scikit-hep/boost-histogram/pull/1035
[#1036]: https://github.com/scikit-hep/boost-histogram/pull/1036

## Version 1.5

### Version 1.5.2

Fix for axis metadata not passing though non-uniform rebinning correctly. Flow
bins are now preserved when doing a non-uniform rebinning. Also adds the
ability to rebin by edges or an existing axis.

This is expected to be the last release with Python 3.8 support. Manylinux
support will likely be bumped from `2024` to `2_28` soon, as well.

#### Features

- Support `edges=` and `axis=` in `bh.rebin` [#977][]
- Allow axis to be passed through `bh.rebin` [#980][], [#982][]

#### Bug fixes

- Axis metadata was broken when rebinning [#978][]
- Flow bins were lost when using variable rebinning [#977][]
- Scikit-build-core 0.11, with PEP 639 license metadata [#986][], [#988][]
- Prepare for an potential upcoming pybind11 3 change [#994][]

#### CI and testing

- Remove extras like `[test]` in favor of dependency-groups [#973][]
- Multithreaded test running [#987][]

[#959]: https://github.com/scikit-hep/boost-histogram/pull/959
[#973]: https://github.com/scikit-hep/boost-histogram/pull/973
[#977]: https://github.com/scikit-hep/boost-histogram/pull/977
[#978]: https://github.com/scikit-hep/boost-histogram/pull/978
[#980]: https://github.com/scikit-hep/boost-histogram/pull/980
[#982]: https://github.com/scikit-hep/boost-histogram/pull/982
[#986]: https://github.com/scikit-hep/boost-histogram/pull/986
[#987]: https://github.com/scikit-hep/boost-histogram/pull/987
[#988]: https://github.com/scikit-hep/boost-histogram/pull/988
[#994]: https://github.com/scikit-hep/boost-histogram/pull/994

### Version 1.5.1

#### Bug fixes

- Make non-uniform rebinning work for Weight() and friends [#972][]

[#972]: https://github.com/scikit-hep/boost-histogram/pull/972

### Version 1.5.0

#### Features

- Support variable rebinning [#913][]
- Removed support for Python 3.7 [#952][]
- Added support for Python 3.13 and free-threaded Python 3.13t [#950][]
- Add GitHub artifact attestations to package distribution [#933][]

#### Backend and docs

- Move build to scikit-build-core [#887][]
- Clean up sdist files [#928][]
- Minor touchup to build backend, use scikit-build-core 0.10+ [#948][]

#### CI and testing

- Try cibuildwheel pyodide [#935][]
- Try to fix pyodide build [#934][]
- Update emscripten build [#937][]
- Bump to Pyodide 3.12 [#938][]
- Speed up pyodide job by a few seconds [#941][]
- Update jobs and noxfile [#929][]
- Use pylint 3.2 github formatter instead [#932][]
- Add some CI speedups [#939][]
- Faster cibuildwheel [#942][]
- Adapt to final release of NumPy 2.1.0 [#951][]

[#887]: https://github.com/scikit-hep/boost-histogram/pull/887
[#913]: https://github.com/scikit-hep/boost-histogram/pull/913
[#928]: https://github.com/scikit-hep/boost-histogram/pull/928
[#929]: https://github.com/scikit-hep/boost-histogram/pull/929
[#932]: https://github.com/scikit-hep/boost-histogram/pull/932
[#933]: https://github.com/scikit-hep/boost-histogram/pull/933
[#934]: https://github.com/scikit-hep/boost-histogram/pull/934
[#935]: https://github.com/scikit-hep/boost-histogram/pull/935
[#937]: https://github.com/scikit-hep/boost-histogram/pull/937
[#938]: https://github.com/scikit-hep/boost-histogram/pull/938
[#939]: https://github.com/scikit-hep/boost-histogram/pull/939
[#941]: https://github.com/scikit-hep/boost-histogram/pull/941
[#942]: https://github.com/scikit-hep/boost-histogram/pull/942
[#948]: https://github.com/scikit-hep/boost-histogram/pull/948
[#950]: https://github.com/scikit-hep/boost-histogram/pull/950
[#951]: https://github.com/scikit-hep/boost-histogram/pull/951
[#952]: https://github.com/scikit-hep/boost-histogram/pull/952

## Version 1.4

### Version 1.4.1

#### Features

- NumPy 2 support. [#918][]
- 32-bit Windows Python 3.12 wheel added (matching NumPy). [#920][]

#### Bugfixes

- Support filling Integer axes with unsigned integers [#917][]
- Avoid triggering NumPy 2 dev release install on Python 3.12. [#914][]

#### Backend and docs

- Add missing API docs [#909][]
- Use boost 1.84 [#920][]

[#909]: https://github.com/scikit-hep/boost-histogram/pull/909
[#914]: https://github.com/scikit-hep/boost-histogram/pull/914
[#917]: https://github.com/scikit-hep/boost-histogram/pull/917
[#918]: https://github.com/scikit-hep/boost-histogram/pull/918
[#920]: https://github.com/scikit-hep/boost-histogram/pull/920

### Version 1.4.0

#### Features

- `overflow=False` is now supported for `IntCategory` and `StrCategory`. [#883][]

#### Changes

- Using `_storage_type` now produces a `DeprecationWarning` instead of `PendingDeprecationWarning`. [#801][]
- Updated Boost to 1.82. The upper limit on Regular axes without overflow is now inclusive like NumPy. [#802][]
- Produce more detailed error messages on C++ errors [#848][]

#### Bugfixes

- Make filling an integer axis with a float array (also) an error. [#876][]
- Include `-latomic` on `armv7l` [#823][]

#### Backend and docs

- Add Python 3.12 support and binary wheels, also latest PyPy. `manylinux2014+` required. [#880][], [#878][]
- Drop Python 3.6 support. [#798][]
- Drop pre-built wheels for 32-bit Linux (NumPy also dropped). [#849][]
- Add testing for WebAssembly (Pyodide). [#850][]
- Use Ruff [#829][]

[#798]: https://github.com/scikit-hep/boost-histogram/pull/798
[#801]: https://github.com/scikit-hep/boost-histogram/pull/801
[#802]: https://github.com/scikit-hep/boost-histogram/pull/802
[#823]: https://github.com/scikit-hep/boost-histogram/pull/823
[#829]: https://github.com/scikit-hep/boost-histogram/pull/829
[#848]: https://github.com/scikit-hep/boost-histogram/pull/848
[#849]: https://github.com/scikit-hep/boost-histogram/pull/849
[#850]: https://github.com/scikit-hep/boost-histogram/pull/850
[#876]: https://github.com/scikit-hep/boost-histogram/pull/876
[#878]: https://github.com/scikit-hep/boost-histogram/pull/878
[#880]: https://github.com/scikit-hep/boost-histogram/pull/880
[#883]: https://github.com/scikit-hep/boost-histogram/pull/883

## Version 1.3

### Version 1.3.2

#### Changes

- Added `storage_type` operator and `storage_type()` function [#781][], with pending deprecation for `_storage_type`. [#786][] [#790][]
- Better errors generated for missing or incorrect sample to mean storage. [#782][]
- Better error message when views are set with an incompatible array. [#794][]

#### Bug fixes

- Patch broken sum with fully empty (0 bin) axis. [#718][]
- Fix zero range `bh.numpy.histogram` to match `numpy.histogram` behavior. [#721][]
- Avoid triggering `__init__` when copying (better support for subclasses with custom init's). [#759][]
- IntCategory now supports numbers larger than 2^24 (now 2^53). [#792][]
- Pick a subset now supported inside a larger expression. [#793][]

#### Backend and docs

- Minor optimizations for UFuncs. [#771][]
- Added Python 3.11 wheels. [#789][]
- Include PyPy 3.9 binary wheels. [#730][]
- Using pybind11 2.10 [#767][]
- Explicit `reset()` documentation. [#783][]
- Minor cleanup and further removal of a little Python 2 back-compat code.
- Warnings have better stacklevel settings.

[#718]: https://github.com/scikit-hep/boost-histogram/pull/718
[#721]: https://github.com/scikit-hep/boost-histogram/pull/721
[#730]: https://github.com/scikit-hep/boost-histogram/pull/730
[#759]: https://github.com/scikit-hep/boost-histogram/pull/759
[#767]: https://github.com/scikit-hep/boost-histogram/pull/767
[#771]: https://github.com/scikit-hep/boost-histogram/pull/771
[#781]: https://github.com/scikit-hep/boost-histogram/pull/781
[#782]: https://github.com/scikit-hep/boost-histogram/pull/782
[#783]: https://github.com/scikit-hep/boost-histogram/pull/783
[#786]: https://github.com/scikit-hep/boost-histogram/pull/786
[#789]: https://github.com/scikit-hep/boost-histogram/pull/789
[#790]: https://github.com/scikit-hep/boost-histogram/pull/790
[#792]: https://github.com/scikit-hep/boost-histogram/pull/792
[#793]: https://github.com/scikit-hep/boost-histogram/pull/793
[#794]: https://github.com/scikit-hep/boost-histogram/pull/794

### Version 1.3.1

#### Bug fixes

- Fixed regression with invalid `.project` input causing segfaults. [#708][]
- Minor skips for specific tests on ppc64le, primarily for a NumPy bug. [#707][]
- Avoid using EH for program control, better on Pyodide. [#709][]
- Fix regression with exact float not being accepted for `.index` for `IntCategory`
  in 1.3.0. Add `hist` nox session to check downstream (manually for the
  moment). [#710][]

[#707]: https://github.com/scikit-hep/boost-histogram/pull/707
[#708]: https://github.com/scikit-hep/boost-histogram/pull/708
[#709]: https://github.com/scikit-hep/boost-histogram/pull/709
[#710]: https://github.com/scikit-hep/boost-histogram/pull/710

### Version 1.3.0

#### User changes

- PyPy 3.8 now supported with binary wheels. [#677][]
- The GIL is released a little more often now. [#662][]
- AxesTuple does not allow construction of non-axes. [#680][]
- KeyError is now thrown when accessing a non-existent item in a Category Axis [#689][]
- WeightedViews now support `np.cumsum` [#699][]

#### Bug fixes

- Fixed WeightedMean storages producing NaN for .variances() [#695][]
- Modify local include slightly to enable WebAssembly compilation in Pyodide [#702][]

#### Developer changes

- Use PyLint in CI to check for some style issues [#690][]
- Developer (CMake) installs no longer require toml [#698][]

[#662]: https://github.com/scikit-hep/boost-histogram/pull/662
[#677]: https://github.com/scikit-hep/boost-histogram/pull/677
[#680]: https://github.com/scikit-hep/boost-histogram/pull/680
[#689]: https://github.com/scikit-hep/boost-histogram/pull/689
[#690]: https://github.com/scikit-hep/boost-histogram/pull/690
[#695]: https://github.com/scikit-hep/boost-histogram/pull/695
[#698]: https://github.com/scikit-hep/boost-histogram/pull/698
[#699]: https://github.com/scikit-hep/boost-histogram/pull/699
[#702]: https://github.com/scikit-hep/boost-histogram/pull/702

## Version 1.2

### Version 1.2.1

#### User changes

- musllinux wheels now provided along with manylinux [#656][]

#### Bug fixes

- Fixed single-element negative growth fill [#654][]

#### Developer changes

- No longer require Docker for clang-format, runs online too [#610][]
- Using pybind11 2.8.0 [#658][]

[#610]: https://github.com/scikit-hep/boost-histogram/pull/610
[#654]: https://github.com/scikit-hep/boost-histogram/pull/654
[#656]: https://github.com/scikit-hep/boost-histogram/pull/656
[#658]: https://github.com/scikit-hep/boost-histogram/pull/658

### Version 1.2.0

#### User changes

- Python 3.10 officially supported, with wheels.
- Support subtraction on histograms [#636][]
- Integer histograms are now signed [#636][]

#### Bug fixes

- Support custom setters on AxesTuple subclasses. [#627][]
- Faster picking if slices are not also used [#645][] or if they are [#648][] (1000x or more in some cases)
- Throw an error when an AxesTuple setter is the wrong length (inspired by zip strict in Python 3.10) [#627][]
- Fix error thrown on comparison with axis and non-axis object [#631][]
- Static typing no longer thinks `storage=` is required [#604][]

#### Developer changes

- Support NumPy 1.21 for static type checking [#625][]
- Use newer Boost 1.77 and Boost.Histogram 1.77+1 [#594][]
- Provide nox support [#647][]

[#594]: https://github.com/scikit-hep/boost-histogram/pull/594
[#604]: https://github.com/scikit-hep/boost-histogram/pull/604
[#625]: https://github.com/scikit-hep/boost-histogram/pull/625
[#627]: https://github.com/scikit-hep/boost-histogram/pull/627
[#631]: https://github.com/scikit-hep/boost-histogram/pull/631
[#636]: https://github.com/scikit-hep/boost-histogram/pull/636
[#645]: https://github.com/scikit-hep/boost-histogram/pull/645
[#647]: https://github.com/scikit-hep/boost-histogram/pull/647
[#648]: https://github.com/scikit-hep/boost-histogram/pull/648

## Version 1.1

### Version 1.1.0

#### User changes

- Experimentally support list selection on categorical axes [#577][]
- Support Python 3.8 on Apple Silicon [#600][]
- Scaling and addition with a scalar affect flow bins too [#580][]
- Change `sum_of_deltas_squared` to `_sum_of_deltas_squared` (was an implementation detail) [#602][]

#### Bug fixes

- Fix "picking" on a flow bin [#576][]
- Better error message on getattr [#596][]

#### Developer changes

- Test on Python 3.10 beta releases [#600][]
- Provide a CMakeLists for quick standalone Boost.Histogram C++ experiments [#591][]
- Adding logging with pytest failure output [#575][]

[#575]: https://github.com/scikit-hep/boost-histogram/pull/575
[#576]: https://github.com/scikit-hep/boost-histogram/pull/576
[#577]: https://github.com/scikit-hep/boost-histogram/pull/577
[#580]: https://github.com/scikit-hep/boost-histogram/pull/580
[#591]: https://github.com/scikit-hep/boost-histogram/pull/591
[#596]: https://github.com/scikit-hep/boost-histogram/pull/596
[#600]: https://github.com/scikit-hep/boost-histogram/pull/600
[#602]: https://github.com/scikit-hep/boost-histogram/pull/602

## Version 1.0

### Version 1.0.2

- Fix scaling a weighted storage [#559][]
- Fix partial summation over a Categorical axis [#564][]
- Support running type checking from Python < 3.8 [#542][]

[#542]: https://github.com/scikit-hep/boost-histogram/pull/542
[#559]: https://github.com/scikit-hep/boost-histogram/pull/559
[#564]: https://github.com/scikit-hep/boost-histogram/pull/564

### Version 1.0.1

#### Subclassing Histogram changes

- A `family=` is no longer required if you _only_ subclass Histogram. [#533][]

#### Bug fixes

- Fix summing of Mean/WeightedMean accumulators [#537][]
- Added missing dependency on `typing_extensions` for Python 3.6 & 3.7 [#529][]

#### Typing changes

- Added Ellipsis support to typing. [#525][]
- Better typing for Views. [#530][]
- Fixed issue with Histogram copy constructor requiring metadata [#532][]

[#525]: https://github.com/scikit-hep/boost-histogram/pull/525
[#526]: https://github.com/scikit-hep/boost-histogram/pull/526
[#529]: https://github.com/scikit-hep/boost-histogram/pull/529
[#530]: https://github.com/scikit-hep/boost-histogram/pull/530
[#532]: https://github.com/scikit-hep/boost-histogram/pull/532
[#533]: https://github.com/scikit-hep/boost-histogram/pull/533
[#537]: https://github.com/scikit-hep/boost-histogram/pull/537

### Version 1.0.0

Dropped support for Python 2 and 3.5; removed large numbers of workarounds.
Fully statically typed. API compatible with the final `0.x` release for most
uses, except for subclassing; subclassing histogram components now uses Python
3 class keyword syntax to set families.

#### User changes

- Dropped Python 2.7 and 3.5 support [#512][]
- Removed deprecated `.options` from axes. Use `.traits` instead. [#503][]
- Full static typing available, UHI 0.1.2+ supported. [#516][], [#517][], [#519][], [#520][], [#521][], [#523][]

#### Subclassing Histogram changes

- Use keyword class family setting when subclassing histogram components
  instead of custom decorator. [#513][]
- Structure of internal repr creation changed and made slightly more public. [#518][]

#### Bug fixes

- Consistently show `metadata=` in repr if present; refactored internal repr handling [#518][]
- Minor typing related fixes for rare bugs (especially in `numpy.py`, [#521][])

[#503]: https://github.com/scikit-hep/boost-histogram/pull/503
[#512]: https://github.com/scikit-hep/boost-histogram/pull/512
[#513]: https://github.com/scikit-hep/boost-histogram/pull/513
[#516]: https://github.com/scikit-hep/boost-histogram/pull/516
[#517]: https://github.com/scikit-hep/boost-histogram/pull/517
[#518]: https://github.com/scikit-hep/boost-histogram/pull/518
[#519]: https://github.com/scikit-hep/boost-histogram/pull/519
[#520]: https://github.com/scikit-hep/boost-histogram/pull/520
[#521]: https://github.com/scikit-hep/boost-histogram/pull/521
[#523]: https://github.com/scikit-hep/boost-histogram/pull/523

## Version 0.13

### Version 0.13.2

- Backport fix scaling a weighted storage
- Backport fix partial summation over a Categorical axis

### Version 0.13.1

- Backport fix for Mean/WeightedMean summing.
- Backport fix for `boost_histogram.numpy` density.
- Backport missing metadata from the repr's.
- Ignore `family=` on Histogram subclassing to make subclassing Histogram only possible in 1.x + 0.x code.

### Version 0.13.0

PlottableProtocol provides a way to plot in different libraries, and easy
access to common quantities. This is expected to be the final release for
Python 2, and mostly equivalent in API to 1.0.

#### User changes

- Support for PlottableProtocol. You can now access `.values()`, `.counts()`,
  and `.variances()` on all storages; used by plotting libraries. `.kind` describes
  the Kind of the histogram (`bh.Kind.COUNT` or `bh.Kind.MEAN`). `.options` has
  been renamed to `.traits`, and a few more useful traits were added, like
  `.discrete`. Most other portions of the Protocol were already present. [#476][]
- Removed deprecated `.rank` on histograms (since 0.8). Use `.ndim` instead. [#505][]
- Supports converting user histogram objects that provide a
  `_to_boost_histogram_` method. [#483][]
- A `view=True` parameter must now be passed to get a View instead of a standard
  NumPy values array from `to_numpy()`. [#498][]

#### Bug fixes

- Added additional support for typing, fixing a couple of rare Python 2 bugs in the process [#493][].
- The resulting histogram from `bh.numpy.*` functions is now reducible [#508][]

#### Developer changes

- Use GitHub Actions for ARM compiling [#474][]
- Apple Silicon support (since 0.12) [#495][]
- Support compiling with C++17 [#502][]
- Rename `NPY_NUM_BUILD_JOBS` to `CMAKE_BUILD_PARALLEL_LEVEL` for consistency
  with other Scikit-HEP projects. [#502][]

[#474]: https://github.com/scikit-hep/boost-histogram/pull/474
[#476]: https://github.com/scikit-hep/boost-histogram/pull/476
[#483]: https://github.com/scikit-hep/boost-histogram/pull/483
[#493]: https://github.com/scikit-hep/boost-histogram/pull/493
[#495]: https://github.com/scikit-hep/boost-histogram/pull/495
[#498]: https://github.com/scikit-hep/boost-histogram/pull/498
[#502]: https://github.com/scikit-hep/boost-histogram/pull/502
[#505]: https://github.com/scikit-hep/boost-histogram/pull/505
[#508]: https://github.com/scikit-hep/boost-histogram/pull/508

## Version 0.12

### Version 0.12.0

Pressing forward to 1.0.

#### User changes

- You can now set all complex storages, either on a Histogram or a View with an
  (N+1)D array [#475][]
- Axes are now normal `__dict__` classes, you can manipulate the `__dict__` as
  normal. Axes construction now lets you either use the old metadata shortcut
  or the `__dict__` inline. [#477][]

#### Bug fixes

- Fixed slicing projection with one-sided slices [#479][]
- Fixed issue if final bin of Variable histogram was infinite by updating to Boost 1.75 [#470][]
- NumPy arrays can be used for weights in `bh.numpy` [#472][]
- Vectorization for WeightedMean accumulators was broken [#475][]

#### Developer changes

- Bumped to pybind11 version [#470][]
- Black formatting used in notebooks too [#470][]

#### Upgrade warning

If you are using `Axis.options`, please transition to `Axis.traits`. `traits`
includes all the old options, along with some new traits, and matches the
PlottableProtocol requirements.

[#470]: https://github.com/scikit-hep/boost-histogram/pull/470
[#472]: https://github.com/scikit-hep/boost-histogram/pull/472
[#475]: https://github.com/scikit-hep/boost-histogram/pull/475
[#477]: https://github.com/scikit-hep/boost-histogram/pull/477
[#479]: https://github.com/scikit-hep/boost-histogram/pull/479

## Version 0.11

### Version 0.11.1

Updating pybind11 to 2.6.0. [#443][] Features:

- Python 3.9 support
- PyPy2 / PyPy3.6 / PyPy3.7 support
- Warnings on latest AppleClang fixed
- 40% faster accumulator fills, simpler implementation
- Segfaults when passing an object with a throwing repr fixed
- kwargs replaced older workarounds (partially at the moment)
- Using new `py::type` instead of `pybind11::detail` usage
- Enhanced CMake support, finds conda and venv now, uses `pybind11_find_import`
- Using setuptools support from pybind11 (previously vendored, so benefits have been available since 0.11.0)

Also cleans up SDists a bit. [#467][]

[#443]: https://github.com/scikit-hep/boost-histogram/pull/443
[#467]: https://github.com/scikit-hep/boost-histogram/pull/467

### Version 0.11.0

A release focused on preparing for the upcoming Hist 2.0 release.

#### User changes

- Arbitrary items can be set on an axis or histogram. [#450][], [#456][]
- Subclasses can customize the conversion procedure. [#456][]

#### Bug fixes

- Fixed reading pickles from boost-histogram 0.6-0.8 [#445][]
- Minor correctness fix [#446][]
- Accidental install of typing on Python 3.5+ fixed
- Scalar ND fill fixed [#453][]

#### Developer changes

- Updated to Boost 1.74 [#442][]
- CMake installs version.py now too [#449][]
- Updated setuptools infrastructure no longer requires NumPy [#451][]
- Some basic clang-tidy checks are now being run [#455][]

[#442]: https://github.com/scikit-hep/boost-histogram/pull/442
[#445]: https://github.com/scikit-hep/boost-histogram/pull/445
[#446]: https://github.com/scikit-hep/boost-histogram/pull/446
[#449]: https://github.com/scikit-hep/boost-histogram/pull/449
[#450]: https://github.com/scikit-hep/boost-histogram/pull/450
[#451]: https://github.com/scikit-hep/boost-histogram/pull/451
[#453]: https://github.com/scikit-hep/boost-histogram/pull/453
[#455]: https://github.com/scikit-hep/boost-histogram/pull/455
[#456]: https://github.com/scikit-hep/boost-histogram/pull/456

## Version 0.10

### Version 0.10.2

Quick fix for extra print statement in fill.

#### Bug fixes

- Fixed debugging print statement in fill. [#438][]

#### Developer changes

- Added CI/pre-commit check for print statements [#438][]
- Formatting CMakeLists now too [#439][]

[#438]: https://github.com/scikit-hep/boost-histogram/pull/438
[#439]: https://github.com/scikit-hep/boost-histogram/pull/439

### Version 0.10.1

Several fixes were made, mostly related to Weight storage histograms from Uproot 4.

#### Bug fixes

- Reduction on `h.axes.widths` supported again [#428][]
- WeightedSumView supports standard array operations [#432][]
- Operations shallow copy (non-copyable metadata supported) [#433][]
- Pandas Series as samples/weights supported [#434][]
- Support NumPy scalars in operations [#436][]

[#428]: https://github.com/scikit-hep/boost-histogram/pull/428
[#432]: https://github.com/scikit-hep/boost-histogram/pull/432
[#433]: https://github.com/scikit-hep/boost-histogram/pull/433
[#434]: https://github.com/scikit-hep/boost-histogram/pull/434
[#436]: https://github.com/scikit-hep/boost-histogram/pull/436

### Version 0.10.0

This version was released during PyHEP 2020. Several improvements were made to
usability when plotting and indexing.

#### User changes

- AxesTuple array now support operations via ArrayTuple [#414][]
- Support `sum` and `bh.rebin` without slice [#424][]
- Nicer error messages in some cases [#415][]
- Made a few properties hidden for accumulators that were not public [#418][]
- Boolean now supports reduction, faster compile [#422][]
- AxesTuple now available publicly for subprojects [#419][]

#### Bug fixes

- Histograms support operations with arrays, no longer take the first element only [#417][]

[#414]: https://github.com/scikit-hep/boost-histogram/pull/414
[#415]: https://github.com/scikit-hep/boost-histogram/pull/415
[#417]: https://github.com/scikit-hep/boost-histogram/pull/417
[#418]: https://github.com/scikit-hep/boost-histogram/pull/418
[#419]: https://github.com/scikit-hep/boost-histogram/pull/419
[#422]: https://github.com/scikit-hep/boost-histogram/pull/422
[#424]: https://github.com/scikit-hep/boost-histogram/pull/424

## Version 0.9

### Version 0.9.0

This version was released just before PyHEP 2020. Several important fixes were made,
along with a few new features to better support downstream projects.

#### User changes

- `metadata` supported and propagated on Histograms (slots added) [#403][]
- Added `dd=True` option in `to_numpy` [#406][]
- Deprecated `cpp` module removed [#402][]

#### Developer changes

- Subclasses can override axes generation [#401][]
- `[dev]` extra now installs `pytest` [#401][]

#### Bug fixes

- Fix `numpy.histogramdd` return structure [#406][]
- Travis deploy multi-arch fixes [#399][]
- Selecting on a bool axes supports 2D+ histograms [#398][]
- Warnings fixed on NumPy 1.19+ [#404][]

[#398]: https://github.com/scikit-hep/boost-histogram/pull/398
[#399]: https://github.com/scikit-hep/boost-histogram/pull/399
[#401]: https://github.com/scikit-hep/boost-histogram/pull/401
[#402]: https://github.com/scikit-hep/boost-histogram/pull/402
[#403]: https://github.com/scikit-hep/boost-histogram/pull/403
[#406]: https://github.com/scikit-hep/boost-histogram/pull/406

## Version 0.8

### Version 0.8.0

This version was released just before SciPy 2020 and Boost 1.74. Highlights
include better accumulator views, simpler summing, better NumPy and Pandas
compatibility, and sums on growing axes. Lots of backend work,
including a new wheel building system, internal changes and better reliance
on Boost.Histogram's C++ tools for actions like cropping.

#### User changes

- Weighted histogram cells can now be assigned directly from iterables [#375][]
- Weighted views can be summed and added [#368][]
- Sum is now identical to the built-in sum function [#365][]
- Adding growing axis is better supported [#358][]
- Slicing an AxesTuple now keeps the type [#384][]
- `ndim` replaces `rank` for NumPy compatibility [#385][]
- Any array-like supported in fill [#391][], any iterable can be used for Categories [#392][]
- Added Boolean axes, from Boost.Histogram 1.74 [#390][]
- Division between histograms is supported [#393][]
- More deprecated functionality removed

#### Bug fixes

- Support older versions of [CloudPickle][] (issue also fixed upstream) [#343][]
- Drop extra printout [#338][]
- Throw an error instead of returning an incorrect result in more places [#386][]

#### Developer changes

- Update Boost to 1.73 [#359][], pybind11 to 2.5.0 [#351][], Boost.Histogram to pre-1.74 [#388][]
- Cropping no longer uses workaround [#373][]
- Many more checks added to [`pre-commit`][] [#366][]
- Deprecating `cpp` interface [#391][]
- Wheelbuilding migrated to [`cibuildwheel`][] and GHA [#361][]

[CloudPickle]: https://github.com/cloudpipe/cloudpickle
[`cibuildwheel`]: https://cibuildwheel.readthedocs.io/en/stable
[`pre-commit`]: https://pre-commit.com
[#338]: https://github.com/scikit-hep/boost-histogram/pull/338
[#340]: https://github.com/scikit-hep/boost-histogram/pull/340
[#343]: https://github.com/scikit-hep/boost-histogram/pull/343
[#351]: https://github.com/scikit-hep/boost-histogram/pull/351
[#358]: https://github.com/scikit-hep/boost-histogram/pull/358
[#359]: https://github.com/scikit-hep/boost-histogram/pull/359
[#361]: https://github.com/scikit-hep/boost-histogram/pull/361
[#365]: https://github.com/scikit-hep/boost-histogram/pull/365
[#366]: https://github.com/scikit-hep/boost-histogram/pull/366
[#368]: https://github.com/scikit-hep/boost-histogram/pull/368
[#373]: https://github.com/scikit-hep/boost-histogram/pull/373
[#375]: https://github.com/scikit-hep/boost-histogram/pull/375
[#384]: https://github.com/scikit-hep/boost-histogram/pull/384
[#385]: https://github.com/scikit-hep/boost-histogram/pull/385
[#386]: https://github.com/scikit-hep/boost-histogram/pull/386
[#388]: https://github.com/scikit-hep/boost-histogram/pull/388
[#390]: https://github.com/scikit-hep/boost-histogram/pull/390
[#391]: https://github.com/scikit-hep/boost-histogram/pull/391
[#392]: https://github.com/scikit-hep/boost-histogram/pull/392
[#393]: https://github.com/scikit-hep/boost-histogram/pull/393

## Version 0.7

### Version 0.7.0

This version removes deprecated functionality, and has several backend
improvements. The most noticeable user-facing change is the multithreaded fill
feature, which can enable significant speedups when you have a dataset that is
much larger than the number of bins in your histogram and have free cores to
use. Several small bugs have been fixed.

#### User changes

- Added `threads=` keyword to `.fill` and NumPy functions; 0 for automatic, default is 1 [#325][]
- `.metadata` is now settable directly from the AxesTuple [#303][]
- Deprecated items from 0.5.x now dropped [#301][]
- `cpp` mode updates and fixes [#317][]

#### Bug fixes

- Dict indexing is now identical to positional indexing, fixes "picking" axes in dict [#320][]
- Passing `samples=None` is now always allowed in `.fill` [#325][]

#### Developer changes

- Build system update, higher requirements for developers (only) [#314][]
  - Version is now obtained from `setuptools_scm`, no longer stored in repo
- Removed `futures` requirement for Python 2 tests
- Updated Boost.Histogram, cleaner code with fewer workarounds

[#301]: https://github.com/scikit-hep/boost-histogram/pull/301
[#303]: https://github.com/scikit-hep/boost-histogram/pull/303
[#314]: https://github.com/scikit-hep/boost-histogram/pull/314
[#317]: https://github.com/scikit-hep/boost-histogram/pull/317
[#320]: https://github.com/scikit-hep/boost-histogram/pull/320
[#325]: https://github.com/scikit-hep/boost-histogram/pull/325

## Version 0.6

### Version 0.6.2

Common analysis tasks are now better supported. Much more complete
documentation. Now using development branch of Boost.Histogram again.

#### Bug fixes

- Fix sum over category axes in indexing [#298][]
- Allow single category item selection [#298][]
- Allow slicing on axes without flow bins [#288][], [#300][]
- Sum repr no longer throws error [#293][]

#### Developer changes

- Now using scikit-hep/azure-wheel-helpers via subtree [#292][]

[#288]: https://github.com/scikit-hep/boost-histogram/pull/288
[#292]: https://github.com/scikit-hep/boost-histogram/pull/292
[#293]: https://github.com/scikit-hep/boost-histogram/pull/293
[#298]: https://github.com/scikit-hep/boost-histogram/pull/298
[#300]: https://github.com/scikit-hep/boost-histogram/pull/300

### Version 0.6.1

Examples and notebooks are now up to date with the current state of the
library. Using Boost 1.72 release.

#### User changes

- Slices and single values can be mixed in indexing [#279][]
- UHI locators supported on axes [#280][]

#### Bug fixes

- Properties on accumulator views now resolve correctly [#273][]
- Division of a histogram by a number is supported again [#278][]
- Setting a histogram with length one slice fixed [#279][]
- NumPy functions now work with NumPy ints in `bins=` [#282][]
- In-place addition avoids a copy [#284][]

[#273]: https://github.com/scikit-hep/boost-histogram/pull/273
[#278]: https://github.com/scikit-hep/boost-histogram/pull/278
[#279]: https://github.com/scikit-hep/boost-histogram/pull/279
[#280]: https://github.com/scikit-hep/boost-histogram/pull/280
[#282]: https://github.com/scikit-hep/boost-histogram/pull/282
[#284]: https://github.com/scikit-hep/boost-histogram/pull/284

### Version 0.6.0

This version fills out most of the remaining features missing from the 0.5.x
series. You can now use all the storages without the original caveats; even
the accumulators can be accessed array-at-a-time without copy, pickled quickly,
and set array-at-a-time, as well.

The API has changed considerably, providing a more consistent experience in
Python. Most of the classic API still works in this release, but will issue a
warning and will be removed from the next release. Please use this release to
transition existing 0.5.x code to the new API.

#### User changes

- Histogram and Axis classes now follow PEP 8 naming scheme (`histogram`->`Histogram`, `regular`->`Regular`, `int`->`Int64` etc.) [#192][], [#255][]
- You can now view a histogram with accumulators, with property access such as `h.view().value` [#194][]
- Circular variable and integer axes added [#231][]
- Split Category into `StrCategory` and `IntCategory`, now allows empty categories when `growth=True` [#221][]
- `StrCategory` fills are safer and faster [#239][], [#244][]
- Added axes transforms [#192][]
- `Function(forward, inverse)` transform added, allowing ultra-fast C function pointer transforms [#231][]
- You can now set histogram contents directly [#250][]
- You can now sum over a range with endpoints [#185][]
- `h.axes` now has the functions from axis as well. [#183][]
- `bh.project` has become `bh.sum` [#185][]
- `.reduce(...)` and the reducers in `bh.algorithm` have been removed in favor of dictionary based UHI slicing [#259][]
- `bh.numpy` module interface updates, `histogram=bh.Histogram` replaces cryptic `bh=True`, and `density=True` is now supported in NumPy mode [#256][]
- Added `hist.copy()` [#218][] and `hist.shape` [#264][]
- Signatures are much nicer in Python 3 [#188][]
- Reprs are better, various properties like `__module__` are now set correctly [#200][]

#### Bug fixes

- Unlimited and AtomicInt storages now allow single item access [#194][]
- `.view()` now no longer makes a copy [#194][]
- Fixes related to string category axis fills [#233][], [#230][]
- Axes are no longer copies, support setting metadata [#238][], [#246][]
- Pickling accumulator storages is now comparable in performance simple storages [#258][]

#### Developer changes

- The linux wheels are now 10-20x smaller [#229][]
- The hist/axis classes are now pure Python, with a C++ object inside [#183][]
- Most internal names changed, `core->_core`, etc. [#183][]
- The `uhi` module is now `tag`. [#183][]
- `boost_histogram.cpp as bh` provides C++ high-compatibility mode. [#183][]
- Indexing tags now use full UHI instead of workarounds [#185][]
- Removed log and sqrt special axes types[#231][]
- Family and registration added, new casting system [#200][]

[#183]: https://github.com/scikit-hep/boost-histogram/pull/183
[#185]: https://github.com/scikit-hep/boost-histogram/pull/185
[#188]: https://github.com/scikit-hep/boost-histogram/pull/188
[#192]: https://github.com/scikit-hep/boost-histogram/pull/192
[#194]: https://github.com/scikit-hep/boost-histogram/pull/194
[#200]: https://github.com/scikit-hep/boost-histogram/pull/200
[#218]: https://github.com/scikit-hep/boost-histogram/pull/218
[#221]: https://github.com/scikit-hep/boost-histogram/pull/221
[#229]: https://github.com/scikit-hep/boost-histogram/pull/229
[#230]: https://github.com/scikit-hep/boost-histogram/pull/230
[#231]: https://github.com/scikit-hep/boost-histogram/pull/231
[#233]: https://github.com/scikit-hep/boost-histogram/pull/233
[#238]: https://github.com/scikit-hep/boost-histogram/pull/238
[#239]: https://github.com/scikit-hep/boost-histogram/pull/239
[#244]: https://github.com/scikit-hep/boost-histogram/pull/244
[#246]: https://github.com/scikit-hep/boost-histogram/pull/246
[#250]: https://github.com/scikit-hep/boost-histogram/pull/250
[#255]: https://github.com/scikit-hep/boost-histogram/pull/255
[#256]: https://github.com/scikit-hep/boost-histogram/pull/256
[#258]: https://github.com/scikit-hep/boost-histogram/pull/258
[#259]: https://github.com/scikit-hep/boost-histogram/pull/259
[#264]: https://github.com/scikit-hep/boost-histogram/pull/264

## Version 0.5

### Version 0.5.2

#### User changes:

- `bh.loc` supports an offset [#164][]
- Nicer reprs in several places [#167][]
- Deprecate `.at` and `.axis` [#170][]

#### Bug fixes:

- Use relative paths in setup.py to avoid resolving WSL paths on Windows [#162][], [#163][]
- Better pybind11 support for Python 3.8 [#168][]

#### Developer changes:

- Serialization code shared with Boost.Histogram [#166][]
- Avoid unused PEP 517 isolation for now [#171][] (may return with proper PEP 518 support eventually)

[#162]: https://github.com/scikit-hep/boost-histogram/pull/162
[#163]: https://github.com/scikit-hep/boost-histogram/pull/163
[#164]: https://github.com/scikit-hep/boost-histogram/pull/164
[#166]: https://github.com/scikit-hep/boost-histogram/pull/166
[#167]: https://github.com/scikit-hep/boost-histogram/pull/167
[#168]: https://github.com/scikit-hep/boost-histogram/pull/168
[#170]: https://github.com/scikit-hep/boost-histogram/pull/170
[#171]: https://github.com/scikit-hep/boost-histogram/pull/171

### Version 0.5.1

#### User changes:

- Removed the `bh.indexed`/`h.indexed` iterator [#150][]
- Added `.axes` AxisTuple, with direct access to properties [#150][]
- Cleaned up tab completion in IPython [#150][]

#### Bug fixes:

- Fixed a bug in the sdist missing Boost.Variant2 [#154][]
- Fixed filling on strided inputs [#158][]

[#150]: https://github.com/scikit-hep/boost-histogram/pull/150
[#154]: https://github.com/scikit-hep/boost-histogram/pull/154
[#158]: https://github.com/scikit-hep/boost-histogram/pull/158
[#159]: https://github.com/scikit-hep/boost-histogram/pull/159

### Version 0.5.0

First beta release and beginning of the changelog.

#### Known issues:

- Unlimited storage does not support pickling or classic multiprocessing
- Some non-simple storages do not support some forms of access, like `.view`
- Indexing and the array versions (such as centers) are incomplete and subject to change
- The numpy module is provisional and subject to change
- Docstrings and signatures will improve in later versions (especially on Python 3)