MC27L Lab 4: Nim with Strategies (Spring 1997)

Due: Wednesday, April 23, at the beginning of class

Introduction

Prelab

In lab

• Using the File menu's Open command, you should open the file:

  /Net/solen/u8/Faculty/ek/karl/Public/MC27/nim.scm
  

  save it somewhere in your directory, and evaluate everything in it. This file contains the Nim program and the game-state implementation from the book, except that computer-move and human-move are modified as indicated in exercise 6.13(c).

• In order to make the Nim program work, you will need an implementation of the move-instruction ADT (exercise 6.13(b)). Since you may be starting this lab before the discussion of how to implement a data type has occurred, we have set up a ``hidden'' implementation of the move-instruction data type. You can access this implementation by evaluating the following load expression:

  (load "/Net/solen/u8/Faculty/ek/karl/Public/MC27/move-instruction")
  

  You should be aware that this is not a file you can open up and read, but instead is a compiled version of the move-instruction ADT implementation. You are required to implement the move-instruction ADT yourself sometime in this lab, but we have set up the lab so that you can start out by simply using the ADT.

  Once you have evaluated and loaded the two files (and be sure that you do so in the order we indicated), you can then play some Nim games with the computer by evaluating, for example, the expression:

  (play-with-turns (make-game-state 5 8) 'human)
  

  Play a couple of games so that you get a hang of how the interaction works.

• At this point, you have two choices: you can either implement the move-instruction ADT (exercise 6.13(b)), or you can go on to later exercises until implementation issues have been discussed in class. (Actually, implementing an ADT is not too terribly difficult, so if you want to read section 6.3 and try your hand at it, please do so). If you decide not to implement the move-instruction ADT now, then go on to the next exercise, but be sure to do exercise 6.13(b) before you finish the lab, probably during the next lab session.

  For your convenience when doing the implementation of the move-instruction ADT, we have included ``stubs'' for the three ADT operations near the bottom of the file; the constructor is called make-move-instruction and the two selectors are called num-coins and pile-number. You should write them correctly by removing the error expressions which they currently contain and replacing them with the actual procedure bodies. You should then test your implementation by playing a game like you did before.

  Keep in mind that make-move-instruction just constructs a move-instruction object, while next-game-state actually performs the move.

• Do exercises 6.14-6.19 in the text. When working with the random procedure, keep in mind that each time you use it you may get a different result; if you want to use the same randomly chosen integer twice, you should hold onto it, for example by naming it with a let, as you won't be able to regenerate it.

• You are encouraged to do exercises 6.20 and 6.21 if you have time, but they are not required.

Postlab

As usual, write up a lab report that explains all of what you did to an audience generally knowledgeable about Scheme and such, but ignorant of specifically what you did. Answer all of the questions posed, but do not simply write up your lab as a sequence of exercises. Instead, try to convey the big picture of what you accomplished. Remember, there are some tips in the document entitled "Suggestions for clear lab reports in computer science courses."