关于std::string相等的比较问题

[anuosix]

有两个string
u和v，运行中的值都是“jane”
然后我用if(u==v)来进行比较，比较结果是不相等，为什么呢？
然后我换了u.compare(v)，还是不行，结果还是不正确，望高手告知
注：是unicode模式

[yshuise]

#include "stdafx.h"
#include <iostream>
#include <string>

int _tmain(int argc, _TCHAR* argv[])
{   
	std::string u = "jane";
	std::string v("jane");
	if(u==v)std::cout<<"good"<<std::endl;
	
	return 0;
}

good
请按任意键继续. . .

[anuosix]

struTmp.u=qstrArr[0].toStdWString();
			struTmp.v=qstrArr[1].toStdWString();		
			struTmp.iNum=1;

			if (struTmp.u.compare(struTmp.v)==0)
			{
				m_vtrUU.push_back(struTmp);
				strCurrentMode=_T("UU");
			}

qstrArr是qt的QString的数组，u和v为结构体struTmp的string类型的成员，这样写出来的代码在执行的时候，明明相等的字符串却不相等
判断相等的那条语句最初使用的是 if(struTmp.u==struTmp.v)

[icosagon]

先把QString类型的u和v比较一下吧，QString内置是utf-8的编码，有可能u和v字符串来源的编码不同

[hua_zhixing_]

应该不会吧,把你的代码帖上看看

[zgjxwl]

应该不会啊。。。。

// StringEqual.cpp
// compile with: /EHsc
// Illustrates how to use the operator== to test for
// equality of a basic_string variable and a
// null-terminated string. It also illustrates how to
// use the operator== to test for equality of two
// basic_string variables.
//
// Functions:
//
//    operator==   returns true if the basic_string and the null-
//                 terminated string are equal.
//    operator==   returns true if both basic_strings are equal.
//////////////////////////////////////////////////////////////////////

#pragma warning(disable:4786)
#include <string>
#include <iostream>

using namespace std ;

void trueFalse(int x)
{
  cout << (x? "True": "False") << endl;
}

int main()
{
   string S1="ABC";
   string S2="ABC";
   string S3="DEF";
   string S4; //This specifies an empty initial-controlled sequence.
   char CP1[]="abc";
   char CP2[]="DEF";
   char *CP3 = NULL;

   cout << "S1 is " << S1 << endl;
   cout << "S2 is " << S2 << endl;
   cout << "S3 is " << S3 << endl;
   cout << "S4 is" << S4 << endl;
   cout << "CP1 is " << CP1 << endl;
   cout << "CP2 is " << CP2 << endl;

   cout << "S1==CP1 returned ";
   trueFalse(S1==CP1);  // False    (calls function 1)

   cout << "S1==CP2 returned ";
   trueFalse(S1==CP2);  // False   (calls function 1)

   cout << "CP1==S1 returned ";
   trueFalse(CP1==S1);  // False    (calls function 2)

   cout << "CP2==S1 returned ";
   trueFalse(CP2==S1);  // False   (calls function 2)

   cout << "S1==S2 returned ";
   trueFalse(S1==S2);   // True    (calls function 3)

   cout << "S1==S3 returned ";
   trueFalse(S1==S3);   // False   (calls function 3)

   cout << "S1==S4 returned ";
   trueFalse(S1==S4);   // False   (calls function 3)

   // Following use of the operator will cause the program to
   // crash since CP3 is NULL.
   // cout << "S1==CP3 returned ";
   // trueFalse(S1==CP3);
}

[anuosix]

这是这个函数的全部代码，谢谢大家!!!

void COperatePairs::countPairTimes(const string &strFileName)
{
	QFile qfileToRead(QString::fromStdWString(strFileName));
	qfileToRead.open(QIODevice::ReadOnly);
	qfileToRead.at(0);
	QString qstrOldLine("");
	QString qstrNewLine("");
	QString qstrU;
	QString qstrV;
	string strU(_T(""));
	string strV(_T(""));
	int iNum=0;
	string strCurrentMode(_T(""));
	if (qfileToRead.atEnd()==false)
	{

		qstrNewLine=qstrOldLine=qfileToRead.readLine();
		struTriad struTmp;
		QStringList qstrList=qstrNewLine.split(",",QString::SkipEmptyParts);
		QString qstrArr[2];
		QStringList::Iterator it=qstrList.begin();
		int i=0;
		for (;it!=qstrList.end();it++)
		{
			qstrArr[i]=*it;
			i++;
		}
		
		struTmp.u=qstrArr[0].toStdWString();
		struTmp.v=qstrArr[1].toStdWString();		
		struTmp.iNum=1;
		if (struTmp.u==struTmp.v)
		{
			m_vtrUU.push_back(struTmp);
			strCurrentMode=_T("UU");
		}
		else
		{
			m_vtrUV.push_back(struTmp);
			strCurrentMode=_T("UV");
		}
	}
	while (qfileToRead.atEnd()==false)
	{
		size_t currentVtrUVSize=m_vtrUV.size();
		size_t currentVtrUUSize=m_vtrUU.size();
		qstrNewLine=qfileToRead.readLine();
		if (qstrNewLine==qstrOldLine)
		{
			if (strCurrentMode==_T("UU"))
			{
				m_vtrUU[currentVtrUUSize-1].iNum++;
			}
			else if (strCurrentMode==_T("UV"))
			{
				m_vtrUV[currentVtrUVSize-1].iNum++;
			}
		}
		else
		{
			struTriad struTmp;
			QStringList qstrList=qstrNewLine.split(",",QString::SkipEmptyParts);
			QString qstrArr[2];
			QStringList::Iterator it=qstrList.begin();
			int i=0;
			for (;it!=qstrList.end();it++)
			{
				qstrArr[i]=*it;
				i++;
			}
			struTmp.u=qstrArr[0].toStdWString();
			struTmp.v=qstrArr[1].toStdWString();		
			struTmp.iNum=1;

			if (struTmp.u.compare(struTmp.v)==0)
			{
				m_vtrUU.push_back(struTmp);
				strCurrentMode=_T("UU");
			}
			else
			{
				m_vtrUV.push_back(struTmp);
				strCurrentMode=_T("UV");
			}
			
		}
		qstrOldLine=qstrNewLine;	
	}
	qfileToRead.close();
}

[anuosix]

函数的功能是从一个文件中读取每一行(每行包含两个字符串，用逗号隔开)，然后统计字符对的个数，我这里是分开统计的，如果一行两个字符串相同，则用一个三元组（u，u，num）表示，不相同使用（u，v，num）表示，u和v代表字符串

[zgjxwl]

[Quote=引用 7 楼 anuosix 的回复:]
函数的功能是从一个文件中读取每一行(每行包含两个字符串，用逗号隔开)，然后统计字符对的个数，我这里是分开统计的，如果一行两个字符串相同，则用一个三元组（u，u，num）表示，不相同使用（u，v，num）表示，u和v代表字符串
[/Quote]

你最好单步跟踪到那里看值到底是不是相同的。

[anuosix]

找到原因了，弱智问题:)
struTmp.u=qstrArr[0].toStdWString();
改成
struTmp.u=qstrArr[0].trimmed().toStdWString();
就可以了

谢谢大家，结贴！！！