As with last week, the assignment is to bring together the lsystem and turtle interpreter classes to make a scene that consists of fractal shapes and trees. Your top-level program will include both the lsystem and interpreter modules. Unlike last week, however, your scene.py may not include the turtle module or make any calls to turtle commands directly. If you want to draw something, you have to pass a string to the interpreter drawString function. There will be no exceptions to that rule. (Note that you may attach arbitrary meaning to any character not used by an L-system grammar.)

Tasks

1. We want to be able to change the color of elements in an Lsystem without affecting the color of other elements. We would also like to avoid setting colors, widths, or other turtle drawing features by adding new parameters to drawString. Modify your drawString function so that it supports five additional characters in the strings.
   • '<' - the left angle bracket should append the current turtle color onto a color stack. You'll need to create a separate colorstack variable similar to the one used for position and heading. You can use the function turtle.color() to get the turtle's current color. Note that this function returns a duple of colors. You should append just the first element of the tuple onto the color stack (e.g. turtle.color()[0] ).
   • '>' - the right angle bracket should pop the current turtle color off the color stack and set the turtle's color to that value.
   • 'g' - set the turtle's color to green (e.g. (0.15, 0.5, 0.2) ).
   • 'y' - set the turtle's color to light yellow ( e.g. (0.8, 0.8, 0.3) ).
   • 'r' - set the turtle's color to red ( e.g. (0.7, 0.2, 0.3) ).

   Once you have made the modifications to drawString, try running systemFL using the classtest.py test function from the lab. You can also use the test function single.py to draw just a single tree.

2. The above simulations use a new character, L, in their drawings. Change your TurtleInterpreter to recognize this character and draw a leaf, which could be drawn as a semicircle or a circle or a line (you do not need to change the color). Go back and run classtest.py. This time your scene will contain a bunch of multi-colored fallen leaves!

3. Create a file make_image2.py and write a function that makes a forest or garden of flowers that includes at least two different multi-rule L-systems with leaves or other ornaments that make use of the color store/restore.The following are variations with leaves and flowers, all defined by strings (no special characters except L). Try to include L-system trees with different numbers of iterations.

   systemCL	systemDL	systemEL	systemFL	systemGL

   This is required image 1.

4. Make two new L-systems. They can be variations on one of the ones provided, an L-system from the ABOP book, or one you create on your own. The L-systems of interest are given in the ABOP book chapter 1, pages 10, 11, and 25.

   If you use a variation, include both the original and your variant in your writeup. (The difference does not have to be large.)

   In the file make_image3.py, create a scene function that makes an image using your L-systems after 2, 3, and 4 iterations. Note, if using a different pattern of iterations is more interesting (e.g. 4, 5, 6) you are free to use a different set of three iteration values. Indicate what you used in your writeup.

   This is required image 2.

Extensions

Each assignment will have a set of suggested extensions. The required tasks constitute about 85% of the assignment, and if you do only the required tasks and do them well you will earn a B+. To earn a higher grade, you need to undertake one or more extensions. The difficulty and quality of the extension or extensions will determine your final grade for the assignment. One complex extension, done well, or 2-3 simple extensions are typical.

• Have each tree exhibit some variation by modifying aspects of how it is drawn.
• Add leaves, berries, or color to your trees by adding symbols to the rules and cases to your turtle interpreter. For each new symbol, you will need another elif case in your drawString function.
• In the Lsystem class create a method def __str__(self) that returns a nicely formatted string that might look like the following when printed.

  base X
  rule X -> F-[[X]+X]+F[+FX]-X
  rule F -> FF
  

  The __str__ function gets called automatically when an object is printed out. It's also called to implement casting an object to a string using str(thing). Note that your __str__ function should not print anything out. It should build a string from the information in your L-system and return the string. Remember that '\n' is how you create a newline character.

  In the test main function the line:

  print lsys

  should print out your nicely formatted string instead of the generic class instance string when you run your lsystem.py file.

  See if you can draw the base string and rule below the image of a tree from that L-system.

• Get fancy with required images 1 or 2. Note that fancy means using programming structures (functions, loops, conditionals, lists, or math) to make a more interesting scene.
• Make more L-systems.
• Demonstrate that you can create other kinds of shapes (like squares, triangles, etc) by passing strings to the turtle interpreter's drawString function.
• Use a Python language feature new to you (not just a new library feature or function)

Writeup and Hand-In

Before handing in your code, double check that it is well-styled:

• All variable names and function names use either camelCase or snake_case.
• All files and functions have docstrings.
• Comments are added to explain complicated code blocks.
• All variable and function names are appropriately descriptive.
• Functions are defined before any other code is added at the top level of each file.
• In a file with any functions defined, top level code is wrapped so that it won't execute if that file is imported by another.

Make a new wiki page for your assignment. Put the label cs151s14project8 on the page. Each of you needs to make your own writeup.

In addition to making the wiki page writeup, put the python files you wrote on the Academics server in your private handin directory.

Colby Wiki

In general, your writeup should follow the outline below.

• A brief summary of the task, in your own words. This should be no more than a few sentences. Give the reader context and identify the key purpose of the assignment.
• A description of your solution to the tasks, including any images you created. (Make sure your images are appropriately sized to fit onto the wiki page.) This should be a description of the form and functionality of your final code. You may want to incorporate code snippets in your description to point out relevant features. Note any unique computational solutions you developed.
• A description of any extensions you undertook, including images demonstrating those extensions. If you added any modules, functions, or other design components, note their structure and the algorithms you used.
• A brief description (1-3 sentences) of what you learned.
• A list of people you worked with, including students who took the course in previous semesters, TAs, and professors. Include in this list anyone whose code you may have seen. If you didn't work with anyone, please say so.
• Don't forget to label your writeup so that it is easy for others to find. For this lab, use cs151s14project8