用algorithm中copy方法复制string中的一段到另一个string中

[share_feelings]

std::string str_temp;

std::string::const_iterator iter_current;
std::string::const_iterator iter_x;
std::string::iterator iter_temp;

iter_temp=str_temp.begin();
std::copy(iter_current,iter_x,iter_temp);

结果编译通过，但是运行出错，调试时说这里复制出错：
Unhandled Exception in tes.exe ox:***** :Aceess Violation

大家看看这是怎么回事？？？？

[nuoshueihe]

一个是const_iterator
一个是iterator
类型不匹配

[nuoshueihe]

std::string str_temp; 
	
	std::string::iterator iter_current; 
	std::string::iterator iter_x; 
	std::string::iterator iter_temp; 
	
	iter_temp=str_temp.begin(); 
std::copy(iter_current,iter_x,iter_temp); 

[lori227]

std::string::const_iterator iter_current;
std::string::const_iterator iter_x;

这两个有赋值吗~

[crst_zh]

[Quote=引用 3 楼 lori227 的回复:]
std::string::const_iterator iter_current;
std::string::const_iterator iter_x;

这两个有赋值吗~
[/Quote]

初值都没赋，你期望它指向哪个呢？

看到内存访问错误第一个就该想到指针

[pengzhixi]

用insert
str_temp.insert(str_temp.begin(),iter_current,iter_x)

[share_feelings]

void StringDeal::PolynomialStringDeal(const std::string& str,std::vector<double>& coeff,std::vector<int>& exp)
{
assert(StringCheck::PolynomialCheck(str)<0);

std::string str_temp;

std::string::const_iterator iter_positive;
std::string::const_iterator iter_negative;
std::string::const_iterator iter_current;
std::string::const_iterator iter_x;
std::string::iterator iter_temp;

iter_current=str.begin();
iter_positive=std::find(iter_current,str.end(),'+');
iter_negative=std::find(iter_current,str.end(),'-');
while(iter_positive!=str.end() || iter_negative!=str.end())
{
std::cout<<*iter_current<<std::endl;
if(iter_positive-iter_negative>0)
{
iter_x=std::find(iter_current,iter_negative,'x');
std::copy(iter_current,iter_x,str_temp.begin());
coeff.push_back(atof(str_temp.c_str()));
if(iter_negative-(iter_x+2)>0)
{
//str_temp.clear();
std::copy(iter_x+2,iter_negative,str_temp.begin());
exp.push_back(atoi(str_temp.c_str()));
}
iter_current=iter_negative;
}
else
{
iter_x=std::find(iter_current,iter_positive,'x');
iter_temp=str_temp.begin();
std::copy(iter_current,iter_x,str_temp.begin());
coeff.push_back(atof(str_temp.c_str()));
if(iter_positive-(iter_x+2)>0)
{
// str_temp.clear();
std::copy(iter_x+2,iter_positive,str_temp.begin());
exp.push_back(atoi(str_temp.c_str()));
}
iter_current=iter_positive;
}
// str_temp.clear();
iter_positive=std::find(iter_current,str.end(),'+');
iter_negative=std::find(iter_current,str.end(),'-');
}
}

这是完整的一个函数，处理多项式的字符串，把系数存入coeff,指数存入exp中。。

[pengzhixi]

std::copy(iter_current,iter_x,bakc_inserter(str_temp));应该可以

[pengzhixi]

std::copy(iter_current,iter_x,back_inserter(str_temp));

[share_feelings]

8楼不行，报错..

[share_feelings]

用insert方法行了。。