E Perl Scripts Used

Out of sheer boredom, I provided the Perl script used to make the diagram seen in figure A.6. It is seen in figure E.1.

#!/usr/bin/perl -w
#
# $Id: perl.tex,v 1.5 2003/07/13 14:52:58 gleepy Exp $
# Generates the coordinates necessary to draw the blowin doors used
# in blowin.tex.
#

$pi = atan2(1, 1) * 4;
$d = 8.0 * $pi / 180.0;  # 8 degrees in radians, half the door angle
$step = 20.0 * $pi / 180.0;

for ($i = -4; $i <= 4; ++$i) {

   $th = $i * $step;  # 20 degree spacing in radians
   $bottom = sin($th - $d) * 60.0 + 60.0;
   $top = sin($th + $d) * 60.0 + 60.0;

   printf("\\put(195,%9.4f){\\line(1,0){10.0000}}\n", $bottom);
   printf("\\put(195,%9.4f){\\line(1,0){10.0000}}\n", $top);
   printf("\\put(195,%9.4f){\\line(0,1){%7.4f}}   %% blow-in door %2d\n",
    $bottom, $top - $bottom, $i);
   printf("\\put(205,%9.4f){\\line(0,1){%7.4f}}\n",
    $bottom, $top - $bottom);
   print "\n";
}

Figure E.1:

Perl script used to make the blow-in doors

The key to making the diagram work is to remember that I am representing a circle in what is called an orthographic projection. I use the basic formulas

where r is the radius of the shape, such that it is drawn with a length of 2r, t is the position of the top of the line, b is the position of the bottom of the line, θ is the angle which the door is centered on, and φ is the angular size of the door. From that, the expression t - b is the length of the two vertical lines for each door.

Appendix EPerl Scripts Used

Appendix E
Perl Scripts Used