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61 lines
2.3 KiB
Plaintext
61 lines
2.3 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 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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* 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`, which is the type of the input values (may be a const reference if the input value is expensive to copy)
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* have the following methods:
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* `int index(value_type x) const`
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* `value_type operator[](int index) const`
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* `const std::string& label() const`
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* `int bin() const`
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* `int shape() const`
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* `bool uoflow() const`
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For full support of all library features, the `axis_type` should also be:
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* streamable, by implementing a free function `std::ostream operator<<(std::ostream&, const axis_type&)`
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* serializable, by implementing a free function `template <class Archive> inline void serialize(Archive& ar, axis_type & axis, 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 ostreamed.
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It is recommended to take a look at [classref boost::histogram::axis_base], which provides part of the aforementioned infrastructure for axis types.
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[endsect]
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[section 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 uniform external type of 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 for `n` bins.
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* have the following methods:
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* `std::size_t size() const`
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* `void increase(std::size_t index)`
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* `void increase(std::size_t index, value_type n)`
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* `value_type value(std::size_t index) const`
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To support weighted fills, two additional methods are required:
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* `value_type variance(std::size_t index) const`
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* `void weighted_increase(std::size_t index, value_type weight)`
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[classref boost::histogram::container_storage] is a simple example of a storage type which does not support weighted fills.
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[endsect]
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[endsect]
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