Math::PlanePath::Rows -- points in fixed-width rows

       This path is rows of a given fixed width.  For example width=7 is

           width => 7

             3  |  22  23  24 ...
             2  |  15  16  17  18  19  20  21
             1  |   8   9  10  11  12  13  14
           Y=0  |   1   2   3   4   5   6   7
                 -------------------------------
                  X=0   1   2   3   4   5   6

   NStart
       The default is to number points starting N=1 as shown above.  An optional "n_start" can give a different
       start, with the same shape.  For example to start at 0,

           n_start => 0, width => 7

             3  |  21  22  23  24 ...
             2  |  14  15  16  17  18  19  20
             1  |   7   8   9  10  11  12  13
           Y=0  |   0   1   2   3   4   5   6
                 -------------------------------
                  X=0   1   2   3   4   5   6

       The only effect is to push the N values around by a constant amount.  It might help match coordinates
       with something else zero-based.

       See "FUNCTIONS" in Math::PlanePath for behaviour common to all path classes.

       "$path = Math::PlanePath::Rows->new (width => $w)"
       "$path = Math::PlanePath::Rows->new (width => $w, n_start => $n)"
           Create and return a new path object.  A "width" parameter must be supplied.

       "($x,$y) = $path->n_to_xy ($n)"
           Return the X,Y coordinates of point number $n in the path.

       "$n = $path->xy_to_n ($x,$y)"
           Return the point number for coordinates "$x,$y".

           $x  and  $y  are  rounded to the nearest integers, which has the effect of treating each point in the
           path as a square of side 1, so a column -0.5 <= x < width+0.5 and y>=-0.5 is covered.

       "($n_lo, $n_hi) = $path->rect_to_n_range ($x1,$y1, $x2,$y2)"
           The returned range is exact, meaning $n_lo and $n_hi are the smallest and biggest in the rectangle.

       <http://user42.tuxfamily.org/math-planepath/index.html>

       Copyright 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 Kevin Ryde

       This file is part of Math-PlanePath.

       Math-PlanePath is free software; you can redistribute it and/or modify it under  the  terms  of  the  GNU
       General  Public  License  as  published  by  the  Free Software Foundation; either version 3, or (at your
       option) any later version.

       Math-PlanePath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without  even
       the  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
       License for more details.

       You should have received a copy of the GNU General Public License along with Math-PlanePath.  If not, see
       <http://www.gnu.org/licenses/>.

perl v5.32.0                                       2021-01-23                         Math::PlanePath::Rows(3pm)

       Math::PlanePath::Rows -- points in fixed-width rows

       Math::PlanePath, Math::PlanePath::Columns

        use Math::PlanePath::Rows;
        my $path = Math::PlanePath::Rows->new (width => 20);
        my ($x, $y) = $path->n_to_xy (123);