// Copyright 2018 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_AXIS_POLYMORPHIC_BIN_HPP
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#define BOOST_HISTOGRAM_AXIS_POLYMORPHIC_BIN_HPP
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namespace boost {
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namespace histogram {
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namespace axis {
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/**
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Holds the bin data of an axis::variant.
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The interface is a superset of the axis::interval_view
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class. In addition, the object is implicitly convertible to the value type,
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returning the equivalent of a call to lower(). For discrete axes, lower() ==
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upper(), and width() returns zero.
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This is not a view like axis::interval_view for two reasons.
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- Sequential calls to lower() and upper() would have to each loop through
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the variant types. This is likely to be slower than filling all the data in
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one loop.
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- polymorphic_bin may be created from a temporary instance of axis::variant,
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like in the call histogram::axis(0). Storing a reference to the axis would
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result in a dangling reference. Rather than specialing the code to handle
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this, it seems easier to just use a value instead of a view.
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*/
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template <class RealType>
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class polymorphic_bin {
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using value_type = RealType;
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public:
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polymorphic_bin(value_type lower, value_type upper)
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: lower_or_value_(lower), upper_(upper) {}
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/// Implicitly convert to bin value (for axis with discrete values).
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operator const value_type&() const noexcept { return lower_or_value_; }
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/// Return lower edge of bin.
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value_type lower() const noexcept { return lower_or_value_; }
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/// Return upper edge of bin.
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value_type upper() const noexcept { return upper_; }
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/// Return center of bin.
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value_type center() const noexcept { return 0.5 * (lower() + upper()); }
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/// Return width of bin.
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value_type width() const noexcept { return upper() - lower(); }
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template <class BinType>
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bool operator==(const BinType& rhs) const noexcept {
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return equal_impl(rhs, 0);
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}
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template <class BinType>
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bool operator!=(const BinType& rhs) const noexcept {
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return !operator==(rhs);
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}
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/// Return true if bin is discrete.
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bool is_discrete() const noexcept { return lower_or_value_ == upper_; }
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private:
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bool equal_impl(const polymorphic_bin& rhs, int) const noexcept {
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return lower_or_value_ == rhs.lower_or_value_ && upper_ == rhs.upper_;
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}
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template <class BinType>
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auto equal_impl(const BinType& rhs, decltype(rhs.lower(), 0)) const noexcept {
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return lower() == rhs.lower() && upper() == rhs.upper();
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}
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template <class BinType>
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bool equal_impl(const BinType& rhs, float) const noexcept {
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return is_discrete() && static_cast<value_type>(*this) == rhs;
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}
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const value_type lower_or_value_, upper_;
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};
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} // namespace axis
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} // namespace histogram
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} // namespace boost
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#endif
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