# Source code for plugins.turtle

```#
##
##  This file is part of pyFormex 1.0.7  (Mon Jun 17 12:20:39 CEST 2019)
##  pyFormex is a tool for generating, manipulating and transforming 3D
##  geometrical models by sequences of mathematical operations.
##  Project page:  http://savannah.nongnu.org/projects/pyformex/
##  Copyright 2004-2019 (C) Benedict Verhegghe (benedict.verhegghe@ugent.be)
##
##  This program is free software: you can redistribute it and/or modify
##  the Free Software Foundation, either version 3 of the License, or
##  (at your option) any later version.
##
##  This program 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 this program.  If not, see http://www.gnu.org/licenses/.
##
"""Turtle graphics for pyFormex

This module was mainly aimed at the drawing of Lindenmayer products
(see :mod:`plugins.lima` and the Lima example).

The idea is that a turtle can be moved in 2D from one position to another,
thereby creating a line between start and endpoint or not.

The current state of the turtle is defined by

- ``pos``: the position as a 2D coordinate pair (x,y),
- ``angle``: the moving direction as an angle (in degrees) with the x-axis,
- ``step``: the speed, as a discrete step size.

The start conditions are: ``pos=(0,0), step=1., angle=0.``

The followin example turtle script creates a unit square::

fd();ro(90);fd();ro(90);fd();ro(90);fd()
"""
from __future__ import absolute_import, division, print_function

import math
deg = math.pi/180.

[docs]def sind(arg):
"""Return the sine of an angle in degrees."""
return math.sin(arg*deg)

[docs]def cosd(arg):
"""Return the cosine of an angle in degrees."""
return math.cos(arg*deg)

[docs]def reset():
"""Reset the turtle graphics engine to start conditions.

This resets the turtle's state to the starting conditions
``pos=(0,0), step=1., angle=0.``, removes everything from the state save
stack and empties the resulting path.
"""
global pos, step, angle, list, save
pos = [0., 0.]
step = 1.
angle = 0.
list=[]
save=[]

[docs]def push():
"""Save the current state of the turtle.

The turtle state includes its position, step and angle.
"""
global save
save.append([pos, step, angle])

[docs]def pop():
"""Restore the turtle state to the last saved state."""
global pos, step, angle, list, save
pos, step, angle = save.pop(-1)

[docs]def fd(d=None, connect=True):
"""Move forward over a step `d`, with or without drawing.

The direction is the current direction.
If `d` is not given, the step size is the current step.

By default, the new position is connected to the previous with a
straight line segment.
"""
global pos, step, angle, list
if d:
step = d
p = [pos + step * cosd(angle), pos + step * sind(angle)]
if connect:
list.append([pos, p])
pos = p

[docs]def mv(d=None):
"""Move over step `d` without drawing."""
fd(d, False)

[docs]def ro(a):
"""Rotate over angle `a`. The new direction is incremented with `a`"""
global pos, step, angle, list
angle += a

[docs]def go(p):
"""Go to position `p` (without drawing).

While the `mv` method performs a relative move, this is an absolute move.
`p` is a tuple of (x,y) values.
"""
global pos, step, angle, list
pos = p

[docs]def st(d):
"""Set the step size."""
global pos, step, angle, list
step = d

[docs]def an(a):
"""Set the angle"""
global pos, step, angle, list
angle = a

[docs]def play(scr, glob=None):
"""Play all the commands in the script `scr`

The script is a string of turtle commands, where each command
is ended with a semicolon (';').

If a dict `glob` is specified, it will be update with the turtle
module's globals() after each turtle command.
"""
for line in scr.split(';'):
if line:
if glob:
glob.update(globals())
eval(line, glob)
else:
eval(line)
return list

reset()

if __name__ == '__main__':
def test(txt):
l = play(txt)
print("%s line segments" % len(l))
print(l)

test("fd();ro(90);fd();ro(90);fd();ro(90);fd()")
test("fd();ro(90);fd();ro(90);fd();ro(90);fd()")
test("reset();fd();ro(90);fd();ro(90);fd();ro(90);fd()")

# End
```