[section:history Revision history]

[heading 4.0 (first boost release)]

* Removed Python bindings, will be developed in separate repository
  github.com/hdembinski/histogram-python
* All axis can be made optionally circular, except category axis
* Removed circular axis (which is just a circular regular axis)
* Added indexed adaptor generator for convenient and fast iteration over histograms
* Support for axes that can grow in range
* Support for axes which accept multiple values (example: hexagonal binning)
* Support for profiles and more generally, arbitrary accumulators in each cell
* Support for serializing to xml archives
* Added compatibility with Boost.Range, Boost.Units, and Boost.Accumulators
* Added deduction guides for axis types and histogram 
* Performance improvements

[heading 3.2 (not in boost)]

* Allocator support everywhere
* Internal refactoring

[heading 3.1 (not in boost)]

* Renamed `bincount` method to `size`
* Support for axes with only overflow and no underflow bin
* category axis now by default has bin for "other" input that does not fall
  into the predefined categories, making it consistent with other axes
* NaN is now consistently put into overflow bin for all axes
* Eliminated warnings about safe internal conversions on MSVC
* Established a cpp house style with corresponding .clang-format file
* Better detection of Python library on all systems
* Improved code coverage by testing more input errors
* Raise ValueError instead of generic RuntimeError in Python on input errors

[heading 3.0 (not in boost)]

* Support for efficient adding of multiple histograms and scaling
* Re-design of category axis as a general mapping between unique values and bins
* Re-design of the bin description an axis returns upon element access
* Interface cleanup and simplification, more consistency between Python and C++ interface
* Iterators for histogram and axes for STL compatibility
* Regular axis in C++: Allowing transforms with state
* Regular axis in Python: Support for all C++ transforms
* Polymorphic axis::any type
* Internal refactoring from boost::mpl and boost::fusion to std::tuple and boost::mp11
* Windows support

[heading 2.0 (not in boost)]

* Added static_histogram (v1.0 only had dynamic_histogram).
* Merged wfill(...) and fill(...) interface.
* Support custom allocators in storage classes.
* Replaced static_storage with array_storage.
* Replaced dynamic_storage with unlimited_storage, which adds the capability to grow the bin counter into a cpp_int, thus avoiding integer overflow completely.
* Serialization uses binary_archive instead of text_archive. The latter is portable, but the performance is terrible.
* Python interface changed: histograms are now iterable, returning axis classes
* Support reduction (removing a subset of axes and returning the equivalent histogram; in other words, those axes are integrated over)

[heading 1.0 (not in boost)]

* First stable version.

[endsect]