52 lines
1.1 KiB
C++
52 lines
1.1 KiB
C++
#pragma once
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#include "property.hpp"
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class Null : public Property
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{
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public:
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friend class Property;
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static constexpr Flags type = Flags::Null;
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Null(const Null&) = delete;
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Null(Null&&) = delete;
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Null operator=(const Null&) = delete;
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bool operator==(const Property& other) const override
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{
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return other.is<Null>();
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}
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bool operator==(const Null&) const
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{
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return true;
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}
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explicit operator bool()
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{
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return false;
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}
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friend std::ostream& operator<<(std::ostream& stream, const Null&)
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{
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return stream << "NULL";
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}
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std::ostream& print(std::ostream& stream) const override
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{
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return operator<<(stream, *this);
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}
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private:
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// the constructor for null is private, it can be constructed only as a
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// value inside the Property class, Property::Null
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Null() : Property(Flags::Null) {}
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};
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// Null is a const singleton declared in class Property
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// it can be used as a type by using Null or as a value by using Property::Null
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const Null Property::Null;
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