docs: public double get( int index ) {
          MatrixType type = mat.getType();
  
          if( type.isReal()) {
              if (type.getBits() == 64) {
                  return ((DMatrixRMaj) mat).data[index];
              } else {
                  return ((FMatrixRMaj) mat).data[index];
              }
          } else {
              throw new IllegalArgumentException("Complex matrix. Call get(int,Complex64F) instead");
          }
      }