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#include <cstddef>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <string>
#include <unordered_set>
#include <utility>
#include <mapbox/variant.hpp>
using namespace mapbox::util;
void test_singleton()
{
using V = variant<int>;
V singleton = 5;
if (std::hash<V>{}(singleton) != std::hash<int>{}(5))
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
}
void test_default_hashable()
{
using V = variant<int, double, std::string>;
V var;
// Check int hashes
var = 1;
if (std::hash<V>{}(var) != std::hash<int>{}(1))
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
// Check double hashes
var = 23.4;
if (std::hash<V>{}(var) != std::hash<double>{}(23.4))
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
// Check string hashes
var = std::string{"Hello, World!"};
if (std::hash<V>{}(var) != std::hash<std::string>{}("Hello, World!"))
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
}
struct Hashable
{
static const constexpr auto const_hash = 5;
};
namespace std {
template <>
struct hash<Hashable>
{
std::size_t operator()(const Hashable&) const noexcept
{
return Hashable::const_hash;
}
};
}
void test_custom_hasher()
{
using V = variant<int, Hashable, double>;
V var;
var = Hashable{};
if (std::hash<V>{}(var) != Hashable::const_hash)
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
}
void test_hashable_in_container()
{
using V = variant<int, std::string, double>;
// won't compile if V is not Hashable
std::unordered_set<V> vs;
vs.insert(1);
vs.insert(2.3);
vs.insert("4");
}
struct Empty
{
};
struct Node;
using Tree = variant<Empty, recursive_wrapper<Node>>;
struct Node
{
Node(Tree left_, Tree right_) : left(std::move(left_)), right(std::move(right_)) {}
Tree left = Empty{};
Tree right = Empty{};
};
namespace std {
template <>
struct hash<Empty>
{
std::size_t operator()(const Empty&) const noexcept
{
return 3;
}
};
template <>
struct hash<Node>
{
std::size_t operator()(const Node& n) const noexcept
{
return 5 + std::hash<Tree>{}(n.left) + std::hash<Tree>{}(n.right);
}
};
}
void test_recursive_hashable()
{
Tree tree = Node{Node{Empty{}, Empty{}}, Empty{}};
if (std::hash<Tree>{}(tree) != ((5 + (5 + (3 + 3))) + 3))
{
std::cerr << "Expected variant hash to be the same as hash of its value\n";
std::exit(EXIT_FAILURE);
}
}
int main()
{
test_singleton();
test_default_hashable();
test_custom_hasher();
test_hashable_in_container();
test_recursive_hashable();
}
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