std::vector : cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&'
c++, c++11, gcc, iostream, stl
Solution
Template-related error messages can be confusing at times. The problem is that the standard library does not define an overload of `operator <<` for inserting `std::vector` (or any other container, for that matter) into a `std::ostream`. So the compiler fails to find a suitable overload for `operator <<`, and reports this failure as best as it's able (which is unfortunately not too good/readable in your case).
If you want to stream an entire container, you can use `std::ostream_iterator` for that:
auto v = std::vector<int>{1, 2, 3};
std::copy(begin(v), end(v), std::ostream_iterator<int>(std::cout, " "));
As for why you're getting precisely this cryptic error, it helps to analyse the full error message:
prog.cpp: In function ‘int main()’:
prog.cpp:13:37: error: cannot bind ‘std::ostream {aka std::basic_ostream<char>}’ lvalue to ‘std::basic_ostream<char>&&’
std::cout << std::vector<int>{1,2,3};
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from prog.cpp:3:
/usr/include/c++/4.8/ostream:602:5: error: initializing argument 1 of ‘std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = std::vector<int>]’
operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
^
There is apparently a template overload of `operator<<` which takes a lhs argument of type `std::ostream&&` and a rhs argument of the templated type; it exists to allow insertion into temporary streams. Since it's a template, it becomes the best match for the expression in your code. However, `std::cout` is an lvalue, so it cannot bind to `std::ostream&&`. Hence the error.
Problem
I encountered a confusing error message when trying to do something as simple as ``` std::cout << std::vector<int>{1,2,3}; ``` which says ``` cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&' int main() { std::cout << std::vector<int>{1,2,3}; } ``` (tested using gcc-4.8.1 with -std=c++11) SO has similar questions like Overloading operator<<: cannot bind lvalue to ‘std::basic_ostream<char>&&’, which is about some user defined class with nested classes. There is also a work around the accepted answer to that question. But I don't know whether this applies to `std::vector`. Can someone explain why this error happens to `std::vector`, and how to interpret it? Thanks