docs: public static void removeColumns( DMatrixRMaj A , int col0 , int col1 )
      {
          if( col1 < col0 ) {
              throw new IllegalArgumentException("col1 must be >= col0");
          } else if( col0 >= A.numCols || col1 >= A.numCols ) {
              throw new IllegalArgumentException("Columns which are to be removed must be in bounds");
          }
  
          int step = col1-col0+1;
          int offset = 0;
          for (int row = 0, idx=0; row < A.numRows; row++) {
              for (int i = 0; i < col0; i++,idx++) {
                  A.data[idx] = A.data[idx+offset];
              }
              offset += step;
              for (int i = col1+1; i < A.numCols; i++,idx++) {
                  A.data[idx] = A.data[idx+offset];
              }
          }
          A.numCols -= step;
      }