prog.cpp: In function 'int main()':
prog.cpp:11:20: error: invalid initialization of reference of type 'const std::array<float, 3u>&' from expression of type 'std::array<float, 2u>'
pretty_print_r3(xs);
^
prog.cpp:5:6: note: in passing argument 1 of 'void pretty_print_r3(const std::array<float, 3u>&)'
void pretty_print_r3(const array<float, 3> &xs) {
^