CS151 HW#5

Tara Davidson '10

Write up:

1. A brief description of the task (in your own words): In this assignment I created a function that can read an L-system from a file in my directory that consists of a base string, a symbol for replacement, rule with which to replace the symbol, the number of times to execute the replacement, the distance to travel for each F symbol, and the angle to turn with each '+' or '-' symbol. This file has all these components on separate lines. To do this, I called drawShapes in my function but I changed drawShapes so that the parameters were now string, distance, and angle. Now my drawShapes function could take a string of shapes and draw them with a given distance and angle that came from a file in my directory. Another addition to my drawShapes function was that now the function could take the characters 'F', '+', and '-' and the turtle would go forward(distance), turn left(angle), and turn right(angle) with those respective characters. The first file I used was systemA.txt, which I downloaded from the CS151 homework site. When I ran my function and entered in systemA.txt for my file, an image was drawn according to the L-system rules from systemA. The image was the same image that the homework site showed. I then changed parts of systemA.txt so that a new image would be drawn. I saved my L-system as systemK.txt and the image was scene5A (shown below). Then I added '[' and ']' to my drawShapes function so that '[' stores the current turtle heading and position and ']' restores the turtle's heading and position. Then I was able to run systemB. I modified systemB to systemD which produced scene5B (shown below). Finally I made one more addition to my drawShapes function. I created a new shape, a very simple leaf, that could be called by the character 'L'. I put 'L' at the beginning of the rule with which to replace the symbol in system B and created scene5C (shown below).
2. Explain how you store and restore the turtle state At the very beginning of my drawShapes funciton I added a variable, memory, and initialized it to an empty list, []. I created a '[' character in my drawShapes function with the purpose to store the current turtle heading and position. By telling the function to append the turtle heading and append the turtle position, this information was added to the list memory. I had to append the list once for heading and again for position with these statements: memory.append(heading()), memory.append(position()). Then I created a ']' character in my drawShapes function with the purpose to restore the turtle heading and position. I was able to do this by telling the function to lift the turtle up, go to the position stored in the memory list, set the heading to the heading in the memory list, and then putting the turtle down.
3. Show the L-system for each of your images
   The L-system for scene5A:
   -FF
   F
   Ft+Ft-Ft-Ft+Ft
   1
   10
   90
   Picture of scene5A:
   
   
   
   The L-system for scene5B:
   FF
   F
   +FF-[-F+F+F]+[+F-F-F]
   3
   5
   22.5
   Picture of scene5B:
   
   
   
   The L-system for scene5C:
   F
   F
   LFF-[-F+F+F+F]+[+F-F-F]
   3
   5
   22.5
   Picture of scene5C:
   
   
   
4. A description of and pictures for any extensions you did I incorporated Extension 3 in scene5A by using my triangle shape and using the color green. I also did Extension 2 and created another L-system to make scene5D (shown below):
   The L-system for scene5D:
   FFF
   F
   +FF-[-F+F+F]+[+F-F-F]
   5
   2
   40
   Picture of scene5D: