< hash_set>等于运算符在VS2010中不起作用 [英] <hash_set> equality operator doesn't work in VS2010

问题描述

示例代码：

std::hash_set<int> hs1; // also i try std::unordered_set<int> - same effect 
std::hash_set<int> hs2;

hs1.insert(15);
hs1.insert(20);

hs2.insert(20);
hs2.insert(15);

assert(hs1 == hs2);

hash_set不会按照哈希函数定义的顺序存储元素...为什么？
请注意，此代码在VS2008中使用stdext :: hash_set。

hash_set doesn't stores elements in some order defined by hash function... why? Please note that this code works in VS2008 using stdext::hash_set.

推荐答案

看起来平等比较被打破对于Visual C ++ 2010中的 hash_set 和 unordered_set 。

It looks like equality comparisons are broken for both hash_set and unordered_set in Visual C++ 2010.

我使用标准的语言为无序容器实现了一个朴素的平等函数引用由Matthieu 来验证它是一个错误（只是为了确保）：

I implemented a naive equality function for unordered containers using the language from the standard quoted by Matthieu to verify that it's a bug (just to be sure):

template <typename UnorderedContainer>
bool are_equal(const UnorderedContainer& c1, const UnorderedContainer& c2)
{
    typedef typename UnorderedContainer::value_type Element;
    typedef typename UnorderedContainer::const_iterator Iterator;
    typedef std::pair<Iterator, Iterator> IteratorPair;

    if (c1.size() != c2.size())
        return false;

    for (Iterator it(c1.begin()); it != c1.end(); ++it)
    {
        IteratorPair er1(c1.equal_range(*it));
        IteratorPair er2(c2.equal_range(*it));

        if (std::distance(er1.first, er1.second) != 
            std::distance(er2.first, er2.second))
            return false;

        // A totally naive implementation of is_permutation:
        std::vector<Element> v1(er1.first, er1.second);
        std::vector<Element> v2(er2.first, er2.second);

        std::sort(v1.begin(), v1.end());
        std::sort(v2.begin(), v2.end());

        if (!std::equal(v1.begin(), v1.end(), v2.begin()))
            return false;
    }

    return true;
}

它返回 hs1 和 hs2 是相等的。 （有人让我知道，如果你发现了一个错误的代码;我没有真正测试它广泛...）

It returns that hs1 and hs2 from your example are equal. (Somebody let me know if you spot a bug in that code; I didn't really test it extensively...)

我会提交一个缺陷报告Microsoft连接。

I'll file a defect report on Microsoft Connect.

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