no operator "<<" matches these operands

[masterinex]

hello,

when i run this code , i am getting this error:

no operator "<<" matches these operands at line 39:

  # include <iostream>
# include <algorithm>
# include <vector>;

using namespace std;

struct studentinfo {
	string name;
	int grade;
};


bool name(const studentinfo & lhs, const studentinfo & rhs)
{
	return lhs.name < rhs.name; 
}


int main()
{

	vector <studentinfo> s;

	studentinfo sinfo;
	sinfo.name = "gg";
	sinfo.grade = 44;

	studentinfo sinfo2;
	sinfo.name = "gga";
	sinfo.grade = 44;

	s.push_back(sinfo);
	s.push_back(sinfo2);

	sort(s.begin(), s.end(), name);

	for (auto x : s)
	{
		cout << x.name << x.grade << endl;
	}



}

[JLBorges]

#include <string>

[thmm]

Why does does the compiler know string but not << for string without including <string> ?

[keskiverto]

That depends on implementation. The <string> could be a mere wrapper file that includes "real headers" and the other wrappers might include (some) of those same "real files".

The standard says what headers we should include. We should not depend on undocumented implementation-specific dependencies.

[Ruski]

JLBorges is right.
Put #include <string> at the beggining of your code and the problem will be solved. :)
Have a nice day, my friend! :)