Hello, there seems a typo when they check the `bool operator==` - https://github.com/softwareQinc/staq/blob/2c095bf1fb85adc752e9f593e4d93d181cf2f917/include/staq/grid_synth/mat_vec_2x2.hpp#L77 In order to check them equal, then `col_` should compare with `other.col_` not `row` I think.