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#include <iostream>
#include <algorithm>
#include <functional>
#include <iterator>
#include <vector>
#include <string>
 
bool check_sz(const std::string &s, std::string::size_type sz)
{
	return s.size() == sz;
}
 
int main()
{
	int sz = 4;
	std::vector<std::string> v = { "x", "zzz", "yy", "tttt" };
 
	auto check = std::bind(check_sz, _1, 3);
}

prog.cpp: In function 'int main()':
prog.cpp:18:35: error: '_1' was not declared in this scope
  auto check = std::bind(check_sz, _1, 3);
                                   ^
prog.cpp:18:35: note: suggested alternative:
In file included from prog.cpp:3:0:
/usr/include/c++/5/functional:782:34: note:   'std::placeholders::_1'
     extern const _Placeholder<1> _1;
                                  ^

Standard output is empty