元组元素是只读的?

>我正在尝试制作一个程序来扫描HRML标签及其属性。

#include<iostream>
#include<string>
#include<string.h>
#include<vector>
#include<algorithm>
#include<cmath>
#include<sstream>
#include<fstream>
#include<list>
#include<numeric>
#include<map>
#include<iterator>
#include<regex>
#include<climits> //#include"matrix.h"
#include<random>
#include<ctime>
#include<iomanip>
#include<set>
using namespace std; 
typedef tuple<string,vector<string>,bool> tagMap;
int main(){
int n;
int q;
cin>>n>>q;
cin.clear();
cin.ignore(std::numeric_limits<int>::max());
set<tagMap> TagHierarchy;
vector<tuple<string,string,string>> tags;
for(int i=0; i<n; ++i){
string ln;
getline(cin,ln);
istringstream is{ln};
string tagId;
is>>tagId;
if(find(tagId.begin(),tagId.end(),'/')!=tagId.end()){
auto it=find_if(TagHierarchy.begin(),TagHierarchy.end(),[&](tagMap e){if(get<0>(e)==tagId)return true;return false;});
get<2>(*it)=false; // Error is here
}
else{
tagId.erase(remove(tagId.begin(),tagId.end(),'<'),tagId.end());
for(auto& e:TagHierarchy){
if(get<2>(e)){//active
vector<string> v=get<1>(e);
v.push_back(tagId);
}
else{//inactive
}
}
TagHierarchy.insert(make_tuple(tagId,vector<string>{},true));
string tagName;
is>>tagName;
char t;
is>>t;
string tagValue;
is>>tagValue;
tagValue.erase(remove(tagValue.begin(),tagValue.end(),'>'),tagValue.end());
tags.push_back(make_tuple(tagId,tagName,tagValue));
}
}

}

问题出在第 45 行，我扫描将标签更改为关闭，它给我以下内容

error: assignment of read-only location 'std::get<2u, {std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, bool}>((* & it.std::_Rb_tree_const_iterator<_Tp>::operator*<std::tuple<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::vector<std::__cxx11::basi|

但是元组不是常量吗？ 我也尝试过范围循环，对于每个循环，但它们都给了我相同的错误。