Week 7 Lab: Go, Robot, Go!

The goal of this project is to get you to use strings much more: defining strings, reading them in, parsing them, indexing into them, etc.

This lab is very similar to lab 6 in which your scribbler reacted to the commands you gave it interactively. In that lab, your code repeatedly asked for an instruction, and then executed that instruction. This time when your program starts it will ask once for a single string that contains a series of commands for the robot to execute. When your loop finishes executing that series of commands, the program is done.

The format of the string is pretty simple:

<command><val><command><val><command><val>...

where <command> is a single letter, and <val> is a two digit number. The acceptable <command>s are:

f - forward
b - backward
l - turn left
r - turn right
B - beep

Here is a good sample input string:

f03l45f10r90b13B03f19

This will tell the robot to go forward for 3 cms, turn left 45 degrees, go forward for 10 cms, turn right 90 degrees, go backward for 13 cms, beep for 3 seconds, and go forward for 19 cms. Notice that all numbers are 2 digits -- if you need a single digit number, you make it two digits by putting a 0 before it. E.g., 03 .

Step 1: Make the lab7 folder

Open up Eclipse, switch to your S:\workspace workspace, and create a new Folder called lab7. Next, Copy the move.py file over from your lab6 folder, or, copy it from moodle where I have made my version available. Then, in the lab7 folder, create a new file called lab7.py.

Next, open lab6.py (your own or the version I have available on moodle) and copy the entire contents of the file to your lab7.py file. A lot of this project is going to be similar. At this point I highly recommend you close any old files you have open, so that you don't accidentally edit them.

Make sure the top of your lab7.py file has:

from move import *
from myro import *

Step 2: Read in an instruction string from the user

• Modify your getCommand() function so it
  • prints out a new description of what the user can enter. (See above.) Note that the user cannot enter B for backward -- it is now used for beep. Also, don't tell the user they can enter upper case letters. For this project, your code can recognize only lower case letters (except for B, which is the beep command). Finally, your code should tell the user to enter 2-digit numbers.
• The rest of the old function is unchanged:
  • Gets the user input string (which looks something like this, remember: B03b10f05r45.)
  • Returns the string.

Copy and paste this code into your ****main**** code in lab7.py:

# ----------------- main code ------------------------
# init("COM40")         # Note that this is commented out, for now.
instr = getCommand()    # get the instruction string
done = False
currIdx = 0             # index into instr string
while not done:
    # code here to get first character (at index currIdx) into a variable cmd
    # code here to get the second and third characters (offset from currIdx) into an 
    #    integer called val
    # code here to print out the cmd and val
    # code here to increment currIdx by 3 (thus preparing for the next time through the loop)
    # code to test if currIdx is greater than or equal to the length of instr. 
    #     If so, set done to True.

The old ***main*** code you copied from lab6.py has the init() call, etc., and while not done code, etc. Remove that code, but keep the big if-elif code. But, then comment out that if-elif code for now. We'll use it later, but for now, let's just comment it out.

Now, replace the comments in the while loop with actual code.. Then, test your code. The robot won't do anything at this point, but you should be able to test it by adding print statements that show you have gotten the instruction correctly, have broken it into the cmd and val correctly, etc.

Step 3: Implement the code to make the robot move

Start uncommenting out your big if-elif-elif-else statement, like in lab6, so that the robot actually performs the commands it has been given. Hints:

• Note that you will need to convert a string like "01" or "90" or "35" into an integer value. Don't forget to do this. You should have done that above already.
• Note that you do not have a "t" command this time. Or a "q" command.
• You should handle bad commands in the command string. However you don't have to handle totally messed up inputs. You can assume the input has the correct format: letter followed by 2 digits, repeatedly. When handling bad input, print out an informative message for the user.
• The B command should call robot.beep(duration, freq1, freq2) Use variable val for the duration. Good values for freq1 and freq2 are 880 and 660, but you can use any values you want. (Note that B is for beep and b is for backward. Make sure B does not make the robot go backward like it did before.)
• Test your code!
  

Step 4: Modularize your Code

• Read all steps below before you do anything.
• Move all the code you just wrote into a function executeInstructions(instr), which you will place in move.py. The definition of the getCommand() function stays in lab7.py.
• executeInstructions(instr) should take the string given by the user as its only argument. The function returns nothing. So, your final main code should be just this, when you are done:
• init("COM40")
• code to call getCommand(), storing the result in a variable called instr.
• executeInstructions(instr)
  

Step 5: Submit your code

• Clean up any code in lab7.py that isn't relevant anymore (code that is commented out, etc.) Make sure your code is well-documented, indented, hospitable, etc. Make sure you have the correct information in it about you, the author.

To submit your final version of lab7.py and move.py, you’ll need to use Windows Explorer.

• Open the Windows Explorer (shortcut: WindowsKey - e)
• Find your lab7.py and move.py files down in your workspace\CS104\lab7.
• Copy lab7.py and move.py.
• Now, navigate to T:\CS104\current\<yourid>\.
• Create a folder there called lab7. (Do NOT call it Lab7 or lab 7 or Lab 7 or IGonnaBeAEngneer. Call it lab7.)
• Look again at the folder you just created. Is it called lab7? If not, grab your ears and flap them while pretending to fly around the room, and then rename the folder lab7.
• Paste the files (lab7.py and move.py) into that folder.

Grading Rubric: 15 points total

10 points: program that runs correctly. 
1 points: correct comments at the top of the file.
4 points: code is clean and neat and uses good comments and variable names. I.e., the code is hospitable.