University of Maine School of Computing and Information Science COS 470/570

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1 University of Maine School of Computing and Information Science COS 470/570 Assignment 1: Lisp and Robot Familiarization Assigned 8/28 Due 9/13 This assignment is meant to familiarize you with the tools you ll need in other assignments this semester. There are two parts, a Lisp assignment and a robot assignment. 1 Lisp Lisp is one of the primary languages used in AI, and most things you will do in this class will be in Lisp. Aside from this, there are other reasons to learn (or review) Lisp. For one thing, it is one of the most rapidly-growing languages in terms of use. In addition, many programs and other languages use concepts and, more often, syntax from Lisp, and some programs use Lisp itself. Also, learning different languages, especially ones that are quite different from ones they know, is a very good thing for computer science majors and it s required for accreditation. And, finally, if past experience is any guide, some of you might find that you fall in love with the language and want to keep using it. What others have said about Lisp: 1 Lisp is a programmable programming language. John Foderaro One of the most important and fascinating of all computer languages is Lisp... Douglas Hofstadter, Gödel, Escher, Bach: an Eternal Golden Braid The greatest single programming language ever designed. Alan Kay Lisp isn t a language, its a building material. Alan Kay Lisp is worth learning for the profound enlightenment experience you will have when you finally get it; that experience will make you a better programmer for the rest of your days, even if you never actually use Lisp itself a lot. Eric S. Raymond, How to Become a Hacker Emacs is written in Lisp, which is the only computer language that is beautiful. Neal Stephenson, In the Beginning was the Command Line 1 From wikiquote 2 via CLiki.

2 Greenspun s Tenth Rule: Any sufficiently complicated C or Fortran program contains an ad hoc informally-specified bug-ridden slow implementation of half of Common Lisp. 1.1 Getting started The first hurdle to using Lisp is finding and installing a Lisp interpreter. While the School has Lisp installed on the cluster in Neville Hall, you will probably want Lisp running on your own computer. Luckily, Lisp is very easy to find and install, whether you use Linux, a Mac, or Windows. The very simplest thing to do is to go to common-lisp.net 3 and download Lispbox 4, a free, preconfigured Lisp environment. This includes the Steel Bank Common Lisp interpreter (SBCL), the Emacs editor, the SLIME Emacs Lisp interface, a library manager (Quicklisp), and a compiler (Clozure). If you are more of a do-it-yourselfer, then you can download a Lisp interpreter and use it with whatever editor you want. (I strongly suggest Emacs, since it is an extraordinarily powerful editor that has a long history of playing nice with Lisp in fact, most of Emacs is written in Lisp.) I use SBCL on my Mac and Allegro Common Lisp on both Mac and Linux. SBCL is free and available from Allegro Common Lisp is an industrial-strength commercial Lisp, but the folks who sell it, Franz, Inc., have been gracious enough to provide a free version. You can get it at Franz s web site 5. I will also pass out a packet of information about using Emacs and Lisp. It is tailored, primarily for historical reasons, toward using Allegro CL. However, much of its information also applies to SBCL. With respect to programming in Lisp, early in the semester, I will have a two-hour Lisp review to help you become familiar (or refamiliarize yourself) with the language. The recommended textbook can also teach you Lisp rather quickly. In addition, there are many on-line resources for learning Lisp. A good place to look for these, and many other things Lisp-related, is at the Common Lisp Wiki, CLiki 6 or at Common-Lisp.net. 1.2 The Assignment For this assignment, you will do each of the following exercises. You will need to format and comment your code as described in the Lisp packet I will pass out. You will turn in your code and examples of it running electronically to cos470@umcs.maine.edu 1. first2: Simple list manipulation. Write a function, first2, that takes a list as its argument and returns the first two elements of that list as a new list. Note: this should return a list, not a dotted pair. For example, > (first2 (a b c d e f)) (a b) In this example and those to follow, the > sign means a Lisp interpreter prompt, with the line after being the result of evaluating the Lisp expression after the prompt

3 2. add1: Simple math. Write a function, add1, that takes an integer as an argument and returns that integer plus listadd: Recursion and iteration. (a) Write a function, listadd1, that will add 1 to each element in a list of integers: > (listadd1 ( )) ( ) This function should use recursion to do this. (b) Write another function, listadd2, that uses mapcar to do the same thing. (c) Write another function, listadd3, that uses one of Lisp s loop constructs (e.g., dolist, dotimes, or loop) to do the same thing. 4. flatten: Complex recursion. Write a recursive function, flatten, that takes as an argument a list that can include embedded lists and returns a list in which the embedded parentheses have been removed i.e., a list whose elements are all of the elements of all of the embedded lists. For example, > (flatten (a (b c) d (e (f (g (h) i))) j)) (A B C D E F G H I J) 5. last2: More complex list manipulation. Write a function, last2, that takes a list as its argument and returns the last two elements, e.g.: > (last2 (a b c d e)) (D E) 6. my-reverse: More complex list manipulation and recursion. Write a function, reverse, that reverses the order of the elements in a list: > (my-reverse (a b c 1 2 3)) (3 2 1 C B A) You must use recursion, and you may not use the built-in reverse function! 7. printlist: Using formatted output. Lisp has a function, format, for producing formatted output that is similar to C s printf facility. Use this function to write a function, printlist, that takes a list as an argument and produces the following output: > (printlist ( )) ;; "..." here replaces First element: 1 ;; the actual elements Second element: 2 Third element: 3 Fourth element: 4 Fifth element: 5 Sixth element: 6 Seventh element: 7 Eighth element: 8 Ninth element: 9 Tenth element: 10 Eleventh element: 11 ;;... etc.... Ninety-ninth element: 99 One hundredth element: 100 NIL CL-USER(15): 3

4 This should work for any list, with any number of elements (which need not be numeric). Note: the words first, second, etc., are ordinal numbers generated by format. Also note that format should be used to automatically capitalize the ordinal numbers. In order to do this problem, you ll need documentation for the format statement. The definitive source is Common Lisp: The Language, 2nd ed. 7, by Guy Steele. 8. copyfile: File IO. Write a function, copyfile, that takes two file names as arguments and copies the contents of the first file to the second. You cannot simply use Lisp s shell interface to get the operating system to do it for you. As in any programming language, you ll need to open and close the files. In Lisp, the easy way to do this is with the with-open-file special form; for example, to open a file foo and read all its contents, you could do: (with-open-file (in "foo" :direction :input) (loop with line with i = 1 until (eql :eof (setq line (read-line in nil :eof))) do (format t "Read line ~s~%" i) (incf i))) In this, in is a stream variable (which doesn t have to have the name in ) that is read from. This form is also used to write to files, with some slight changes, e.g.: (with-open-file (out "bar" :direction :output :if-exists :supersede :if-does-not-exist :create)...) You can use read to read an entire Lisp expression and write or print to write such an expression. You can read a line at a time with read-line and write an entire line with write-line. 2 Robots There are some very simple robots available for the class. Later, we will use them at least as simple agents, and hopefully for more as the semester progresses. This assignment will familiarize you with the robot Scribbler/Fluke robots. The robots we have were developed by Georgia Robotics (associated with Georgia Tech and Bryn Mawr College) for teaching introductory computer science. They are based on a very simple robot body, Parallax s Scribbler. By itself, the Scribbler robot from Parallax 8, has a very simple on-board computer, a BASIC Stamp. This is a microcontroller that is programmed using PBASIC. It has several sensors, including light sensors, IR (infrared) detectors, and a line detector (for line-following behavior). Effectors are primarily the wheels, but also some LEDs and a speaker. To this, Georgia Robotics added an IPRE (Institute for Personal Robots in Education) Fluke 9 board. This adds some additional IR sensors for object detection, some additional LEDs, and a color camera. Due to the configuration of the robot, the Fluke board mounts on the back, which means that the back of the robot now becomes the front. A benefit of this is that the robot + board now has IR sensors on the front and back. However, the biggest benefit of the board is that it adds Bluetooth communication. This is used to enable communication with an off-robot computer, such as a laptop, that can then remotely wiki.roboteducation.org 4

5 control the robot. The user can write programs in Python to control the robot, using the Myro robot control software 10. In this assignment, you will use Python to control the robot. However, I am currently in the process of writing a Lisp-to-Python interface that will allow your AI programs in future, written (of course) in Lisp, to interface with the robot directly. (If you choose to use a robot for your final project, then for that you may control it using either language.) 2.1 Getting Started First, you will need to check out a robot from me. It is likely, given the size of the class, that you will have a robot all to yourself. Otherwise, you may be asked to share. Your primary on-line resource for setting up and using the robot is the Wiki created by Institute for Personal Robots in Education 11 (IPRE), a joint project of Georgia Tech, Bryn Mawr College, and Microsoft research. The URL for this Wiki is: wiki.roboteducation.org In particular, you will find information on the Wiki about how to install Myro on your computer. There are instructions for Windows, Mac OS, and Linux. You will also find a version of the Myro reference manual that comes in print form with the robots. 2.2 The Assignment Your assignment is simple: set up and get familiar with a Scribbler/Fluke robot. Since we have only a few robots that are not in use already, you will need to share a robot with a partner. You may choose to work on the assignment together, or work individually, sharing the robot. The parts of this assignment are: 1. Check out a robot from me. 2. Install the Myro software on your computer. 3. Upgrade the firmware of the robot, if needed. (Instructions about how to do this are provided in the installation instructions.) 4. Make the robot execute the following algorithm: Begin: For i from 1 to 4 do: Take a picture and display it. Move 2 meters forward. Turn 90 degrees right. end for; end. 5. Make the robot do something cool. There s not much to turn in for this: just a short ( 1 page, probably) write-up noting any problems you had and telling me what cool thing you got the robot to do. Turn this in electronically. If you want, you can also turn in (via or by posting on a Web site) a video of the cool assignment. 10 wiki.roboteducation.org/myro_reference_manual 11 wiki.roboteduction.org/institute_for_personal_robots_in_education 5