Homework 9a

home work!

Programming Language #lang htdp/isl+



Due Date Tues at 9:00pm (Week 9)

Purpose Revise Shannon, and turn it into a game.


Exercise 1 All of your games were at least several hundred lines of code; some were quite a bit more. Some of them worked perfectly, others partially worked. Some had extensive tests, others very few. This exercise involve several parts, all aimed towards improving your existing code:

A. Incorporate feedback given in grading. That might have involved breaking massive functions into appropriately sized helper functions, reformatting code, etc.

B. Pay particular attention to testing. If your parse-cell and parse-grid functions were not useful for testing, please extend them so that you can use them in your tests (e.g., you should be able to use them for both the inputs & outputs of your functions): they should make your tests much more concise and easy to read. If they don’t, pick a different format to parse from (you do not have to change your grid definition: parsing converts, so can handle a different representation).

C. If your code was not fully functional to the point of supporting Homework 6b, please fix whatever outstanding bugs that it has. If it didn’t have enough tests, add them.

D. Organize the file to collect together data definitions, parsing functions, grid functions, etc. Using large comments like:




can make scrolling through the file much easier.

E. If there are any other changes you think could make your code easier to read or understand, please make them (note: aside from comments like in (D) and purpose statements, we do not want you to add other comments—if you find yourself wanting to explain a function, it may indicate that the function is doing too much: splitting it into smaller functions is much better, as they, unlike comments, can never become out of sync with the code).

This should result in significant changes to your code: we will be grading it based on the difference between what you submitted in 6B and here. If you make only a few cosmetic changes, very likely, you will get a very low score.

At the end of it, you should be happy if we decide to project your code in front of the whole class and have you describe how it works.


Exercise 2 Your next task is to turn Shannon into a game. First, update your game world state so that it supports a goal, which should be a set of inputs/outputs. e.g., you might want to be able to represent

X:+,Y:+ -> Z:-

X:+,Y:- -> Z:+

X:-,Y:+ -> Z:+

X:-,Y:- -> Z:+

This is a table version of the function (lambda (X Y) (not (and X Y))), assuming the only values you have are booleans and "+" (positive) corresponds to #true and "-" (negative) corresponds to "false". While we show that one example as a function, you need to represent them in this "relational" form, since you need to support multiple outputs (otherwise, with only booleans, there are limits in how interesting things get), and you need not include all combinations of inputs. e.g., you should be able to equally represent this as a set of goals:

R:+,S:+ -> T:-,U:+

R:-,S:- -> T:+,U:+

You can assume that whoever constructs the goals will do so with inputs/outputs that exist in the grid.

These are goals because each corresponds to a possible simulation of the circuit: i.e., consider the first case of the first example. It indicates that if we set the inputs X and Y to +, then after running the circuit, the output Z should have charge -. In addition to the goal itself, you probably want to record whether or not the goal has been simulated and what the result was.

Exercise 3 You should make a new to-draw handler that, in addition to showing the grid, also shows the goals and whether they have been satisfied. We would suggest that you don’t edit your old draw handler, but rather, make your new one treat it as a helper (depending on how you updated your world state, this is hopefully easy!).

Exercise 4 Now that you have a goal, you should create a new on-tick handler that proceeds through the goals one at a time, running the simulation until it has stopped changing and recording whether the particular goal was sucessful or not. It is fine if short-circuits cause the game to exit out. (As with the to-draw, we would suggest that you have your new handler call the old one as a helper.)

Exercise 5 Finally, update your main function, and be sure you have some visual indication, once all the goals have been run, whether the game was won or lost.

Exercise 6 In order to play the game, a player must configure an initial state of the grid with gates that they believe will satisfy all the goals. Please make two "puzzles": states with just inputs, outputs, and the set of goals. You should use your parse-grid function, and be sure your goals are readable (make a parse-goal function if necessary) so that a player can understand what they are supposed to fill in. You should then also provide solutions (filled in versions of the states) to each of your puzzles. Your puzzles should not be trivial, but you do not have to make them too large (roughly 10x10 grids are probably about right, with a few inputs and outputs).