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59 lines
2.8 KiB
Plaintext
59 lines
2.8 KiB
Plaintext
[section Concepts]
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Users can extend the library with new axis and storage types.
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[section:axis Axis type]
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An `axis_type` converts input values into bin indices.
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An `axis_type` is required to:
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* derive from [classref boost::histogram::axis::axis_base] or [classref boost::histogram::axis::axis_base_uoflow]
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* be default/copy/move constructable
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* be copy/move assignable
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* be equal comparable
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* have a nested type `value_type` reflecting the type of the input values (may be a const reference if the input value is expensive to copy)
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* have a nested type `bin_type`, which is a type that represents the bin, typically a semi-open interval (may be a const reference if the bin type is expensive to copy)
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* have the following methods:
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* `int index(value_type x) const`: takes an input value and returns the bin index
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* `bin_type operator[](int index) const`: takes an index and returns the corresponding bin instance
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* optionally, be streamable by implementation a free function
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* `std::ostream operator<<(std::ostream&, const axis_type&)`
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* optionally, be serializable, by implementing a member function template
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* `template <class Archive> void serialize(Archive& ar, unsigned /* version */)`
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The latter two are not needed, if the histogram that uses the custom axis type is never serialized or streamed.
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It is recommended to take a look at the existing axis types, like [classref boost::histogram::axis::integer], which serve as templates to create new ones.
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[endsect]
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[section:storage Storage type]
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A `storage_type` handles memory for the bin counters and provides a uniform interface for incrementing bin counters and reading their values.
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A `storage_type` is required to:
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* be default/copy/move constructable
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* be copy/move assignable
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* be equal comparable
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* have a nested type `value_type`, the external type used to represent the bin count (internally it may be a different type)
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* have a constructor `storage_type(std::size_t n)`, which prepares the storage of `n` bins.
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* have the following methods and operators:
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* `std::size_t size() const`
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* `void increase(std::size_t index)`
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* `void add(std::size_t index, const value_type& n)`
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* `void add(std::size_t index, const value_type& value, const value_type& variance)`
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* `value_type value(std::size_t index) const`
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* `value_type variance(std::size_t index) const`
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* `storage_type& operator+=(const storage_type& other)`
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* `storage_type& operator*=(const value_type x)`
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* optionally, it can have a method to support weighted fills:
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* `void weighted_increase(std::size_t index, const value_type& weight)`
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[classref boost::histogram::array_storage] is a simple storage type which does not support weighted fills. It may serve as a template to create a new storage type.
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[endsect]
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[endsect]
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