80 lines
2.0 KiB
C++
80 lines
2.0 KiB
C++
#include <cstdlib>
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#include <functional>
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#include <iostream>
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#include <type_traits>
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#include <typeinfo>
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#include <utility>
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#include <vector>
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#include <mapbox/variant.hpp>
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using namespace mapbox;
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namespace test {
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struct point
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{
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public:
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point(double x_, double y_)
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: x(x_), y(y_) {}
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double x;
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double y;
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};
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struct line_string : std::vector<point>
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{
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};
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struct polygon : std::vector<line_string>
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{
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};
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using variant = util::variant<std::reference_wrapper<const point>,
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std::reference_wrapper<const line_string>,
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std::reference_wrapper<const polygon>>;
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struct print
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{
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using result_type = void;
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void operator()(point const& pt) const
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{
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std::cerr << "Point(" << pt.x << "," << pt.y << ")" << std::endl;
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}
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void operator()(line_string const& line) const
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{
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std::cerr << "Line(";
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bool first = true;
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for (auto const& pt : line)
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{
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if (!first) std::cerr << ",";
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std::cerr << pt.x << " " << pt.y;
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if (first) first = false;
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}
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std::cerr << ")" << std::endl;
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}
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template <typename T>
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void operator()(T const& val) const
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{
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std::cerr << typeid(T).name() << std::endl;
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}
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};
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}
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int main()
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{
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std::cerr << sizeof(test::polygon) << std::endl;
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std::cerr << sizeof(test::variant) << std::endl;
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test::point pt(123, 456);
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test::variant var = std::cref(pt);
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util::apply_visitor(test::print(), var);
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test::line_string line;
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line.push_back(pt);
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line.push_back(pt);
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line.push_back(test::point(999, 333));
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var = std::cref(line);
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util::apply_visitor(test::print(), var);
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std::cerr << "Is line (cref) ? " << var.is<std::reference_wrapper<test::line_string const>>() << std::endl;
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auto const& line2 = var.get<test::line_string>(); // accessing underlying type of std::reference_wrapper<T>
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test::print printer;
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printer(line2);
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return EXIT_SUCCESS;
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}
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