下面这个代码出现invalid use of member (did you forget the `&' ?) 错误是什么意思啊

[a530877647]

#include<iostream>
#include<vector>
#include<string>
#include<cctype>
using namespace std;
int main(){
vector<string> svec;
string str;
cout<<"Enter text(Ctrl+Z to end):"<<endl;
while(cin>>str)
svec.push_back(str);
if(svec.size()==0){
cout<<"no strings?"<<endl;
return -1;
}
cout<<"Transformed elements frome the vector:"
<<endl;

for(vector<string>::size_type ix=0;ix!=svec.size();++ix){
for(string::size_type index=0;index!=svec[ix].size;++index)\\错误在这一行
if(islower(svec[ix][index])
svec[ix][index]=toupper(svec[ix][index]);
cout<<svec(ix)<<" ";
if((ix+1)%8==0) cout<<endl;
}
system("pause");
return 0;
}

[zhaoZero41]

for(string::size_type index=0;index!=svec[ix].size();++index)