比较deques时的问题 [英] Problem when comparing deques

问题描述

我在尝试编写两个自制结构的deques时遇到了一些困难。

这是我的结构和双端声明：

I''m having some difficulties when trying to comapare two deques of a selfmade struct.
This is my struct and the deque declaration:

class iterator
{
public:
struct PosPtrs
{
    NodeLevel Level;
    TreeElement Element;
    bool operator ==(const PosPtrs& input)
    {
        return Level == input.Level && Element == input.Element;
    }
    bool operator== (PosPtrs& input)
    {
        return Level == input.Level && Element == input.Element;
    }
};
std::deque<PosPtrs> TreeHistory;
private:
....
};

当尝试

When Trying

iterator it1;
iterator it2;
return it1.TreeHistory == it2.TreeHistory;

我收到编译器错误C2678：



d：\program files\microsoft visual studio 10.0 \vc\include\xutility（2990）：error C2678：binary''= =''：没有找到哪个运算符带有''const BaseTree :: iterator :: PosPtrs''类型的左手操作数（或者没有可接受的转换）

1> d：\program files\microsoft sdks\windows\v7.0a\include\guiddef.h（192）：可能是''int operator ==（const GUID&，const GUID&）' '[使用参数依赖查找找到]

1> d：\program files\microsoft visual studio 10.0 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ ;）''

1> d：\ program files \ microsoft visual studio 10.0 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ '

1> d：\program files\microsoft visual studio 10.0 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ '

1> d：\program files\microsoft visual studio 10.0 \vc\include\system_error（408）：或''bool std :: operator ==（const std :: error_code&，const std :: error_condition& ;）''

1> d：\program files\microsoft visual studio 10.0 \vc\include\system_error（416）：或''bool std :: operator ==（const std :: error_condition&，const std :: error_code& ;）''

1> d：\users\maxime \documents\visual studio 2010\projects\regfilehook\regfilehook\xmlfilereadwrite.h（156）：或''bool BaseTree :: iterator :: PosPtrs :: operator == （const BaseTree :: iterator :: PosPtrs&）''

1> d：\users\maxime \documents\visual studio 2010 \projects\regfilehook \regfilehook \ xmlfilereadwrite.h（160）：或''bool BaseTree :: iterator :: PosPtrs :: operator == （BaseTree :: iterator :: PosPtrs&）''

1>尝试匹配参数列表''（const BaseTree :: iterator :: PosPtrs，const BaseTree :: iterator :: PosPtrs）''

1> ....



最后几行令我困惑。编译器尝试将运算符++（）函数的参数列表与2个参数进行匹配？我找了一个运算符==总是定义只有一个参数（尝试这也没有帮助，它在编译器错误中结束就像预期的那样）..



先谢谢

I get a compiler error C2678:

d:\program files\microsoft visual studio 10.0\vc\include\xutility(2990):error C2678: binary ''=='' : no operator found which takes a left-hand operand of type ''const BaseTree::iterator::PosPtrs'' (or there is no acceptable conversion)
1> d:\program files\microsoft sdks\windows\v7.0a\include\guiddef.h(192): could be ''int operator ==(const GUID &,const GUID &)'' [found using argument-dependent lookup]
1> d:\program files\microsoft visual studio 10.0\vc\include\exception(470): or ''bool std::operator ==(const std::_Exception_ptr &,const std::_Exception_ptr &)''
1> d:\program files\microsoft visual studio 10.0\vc\include\exception(475): or ''bool std::operator ==(std::_Null_type,const std::_Exception_ptr &)''
1> d:\program files\microsoft visual studio 10.0\vc\include\exception(481): or ''bool std::operator ==(const std::_Exception_ptr &,std::_Null_type)''
1> d:\program files\microsoft visual studio 10.0\vc\include\system_error(408): or ''bool std::operator ==(const std::error_code &,const std::error_condition &)''
1> d:\program files\microsoft visual studio 10.0\vc\include\system_error(416): or ''bool std::operator ==(const std::error_condition &,const std::error_code &)''
1> d:\users\maxime\documents\visual studio 2010\projects\regfilehook\regfilehook\xmlfilereadwrite.h(156): or ''bool BaseTree::iterator::PosPtrs::operator ==(const BaseTree::iterator::PosPtrs &)''
1> d:\users\maxime\documents\visual studio 2010\projects\regfilehook\regfilehook\xmlfilereadwrite.h(160): or ''bool BaseTree::iterator::PosPtrs::operator ==(BaseTree::iterator::PosPtrs &)''
1> while trying to match the argument list ''(const BaseTree::iterator::PosPtrs, const BaseTree::iterator::PosPtrs)''
1> ....

The last lines are confusing me. The compiler tries to match an argument list of a operator++() function with 2 arguments? I tought an operator== was always defined with only one argument (trying this doesn''t helps either, it ends like expected in a compiler error)..

Thanks in Advance

推荐答案

class iterator
{
public:
struct PosPtrs
{
    NodeLevel Level;
    TreeElement Element;
    bool operator ==(const PosPtrs& input) const
    {
        return Level == input.Level && Element == input.Element;
    }
};
std::deque<posptrs> TreeHistory;
private:
....
};

线索来自这条消息：

d：\program files\microsoft visual studio 10.0 \vc\include\xutility（2990）：错误C2678：二进制''==''：没有找到哪个运算符带有''const BaseTree :: iterator :: PosPtrs''类型的左手操作数（或者没有可接受的转换）



你的左手操作数也需要是const。

The clue comes from this message:
d:\program files\microsoft visual studio 10.0\vc\include\xutility(2990):error C2678: binary ''=='' : no operator found which takes a left-hand operand of type ''const BaseTree::iterator::PosPtrs'' (or there is no acceptable conversion)

Your left hand operand needs to be const also.

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