doc/guile-example.py

   1 # Guile example: A Logo-like tortoise drawer
   2 # Copyright (C) David Drysdale, Daniel Kraft
   3 # Copyright (C) 2013-2020 Roland Lutz
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation; either version 2 of the License, or
   8 # (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License
  16 # along with this program; if not, write to the Free Software Foundation,
  17 # Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18
  19 # This example shows how to embed Guile as a script interpreter into a
  20 # Python application using the xorn.guile module.  It defines a set of
  21 # functions for controlling a drawing tortoise, makes them available
  22 # by calling xorn.guile.define which creates a top-level Scheme
  23 # binding for each function, and then runs the example script file
  24 # `guile-example.scm' using xorn.guile.load.
  25 #
  26 # In order to run this example, the built Xorn packages need to be in
  27 # your PYTHONPATH.  This means you have to either
  28 # - build Xorn and add the directory `built-packages' inside the build
  29 #   tree to your PYTHONPATH,
  30 # - build and install Xorn and add PREFIX/lib/python2.7/site-packages
  31 #   to your PYTHONPATH, or
  32 # - build and install Xorn to a default prefix (usually /usr/local).
  33
  34 import math, subprocess, sys
  35 import xorn.guile
  36
  37 WIDTH = 10
  38 HEIGHT = 10
  39
  40 pipe = None
  41
  42 x = 0.
  43 y = 0.
  44 direction = 0.
  45 pendown = True
  46
  47 def draw_line(x1, y1, x2, y2):
  48     pipe.write("plot [0:1] %f + %f * t, %f + %f * t notitle\n" % (
  49         x1, x2 - x1, y1, y2 - y1))
  50     pipe.flush()
  51
  52 def tortoise_reset():
  53     global x, y, direction, pendown
  54     x = y = 0.
  55     direction = 0.
  56     pendown = True
  57
  58     pipe.write("clear\n")
  59     pipe.flush()
  60
  61 def tortoise_pendown():
  62     global pendown
  63     result = pendown
  64     pendown = True
  65     return result
  66
  67 def tortoise_penup():
  68     global pendown
  69     result = pendown
  70     pendown = False
  71     return result
  72
  73 def tortoise_turn(degrees):
  74     global direction
  75     direction += math.pi / 180. * degrees
  76     return direction * 180. / math.pi
  77
  78 def tortoise_move(length):
  79     global x, y
  80     newX = x + length * math.cos(direction)
  81     newY = y + length * math.sin(direction)
  82
  83     if pendown:
  84         draw_line(x, y, newX, newY)
  85
  86     x = newX
  87     y = newY
  88     return x, y
  89
  90 if __name__ == '__main__':
  91     p = subprocess.Popen(['gnuplot'], stdin = subprocess.PIPE)
  92     pipe = p.stdin
  93
  94     pipe.write("set multiplot\n")
  95     pipe.write("set parametric\n")
  96     pipe.write("set xrange [-%d:%d]\n" % (WIDTH, WIDTH))
  97     pipe.write("set yrange [-%d:%d]\n" % (HEIGHT, HEIGHT))
  98     pipe.write("set size ratio -1\n")
  99     pipe.write("unset xtics\n")
 100     pipe.write("unset ytics\n")
 101     pipe.flush()
 102
 103     xorn.guile.define('tortoise-reset', tortoise_reset)
 104     xorn.guile.define('tortoise-penup', tortoise_penup)
 105     xorn.guile.define('tortoise-pendown', tortoise_pendown)
 106     xorn.guile.define('tortoise-turn', tortoise_turn)
 107     xorn.guile.define('tortoise-move', tortoise_move)
 108
 109     xorn.guile.load('guile-example.scm')
 110
 111     sys.stdin.readline()