Ch3 A Rule-Based Game

The game of Craps is played with two dice. Read about street craps but ignore the betting.

You are going to create a rule-based craps simulator.

You begin with a set of rules. Our rules will be a list of 3-tuples (point roll outcome):

• point is the current point value (0 at the start),
• roll is the current roll, and
• outcome is +1 for a win, -1 for a loss and 0 if the game continues.

For example: (3 7 -1) indicates that the rule applies when trying to get a point of 3, if the current roll is a 7, then the game is lost.

The rules will include a symbol POINT which is replaced by the current value of the point wherever it occurs, so you can say “getting the same value as the point” by using the rule:

(POINT POINT 1)

Think: How would you use POINT to indicate that rolling a 7 when you are trying for any other number results in a loss?

Technical Orientation

You will define a list of rules:

(defparameter *CRAPS-RULES* '((0 7 1) (POINT POINT 1) ...))

1. Write a function simulate-1 that takes in the current point value as well as the current roll total, and puts out an outcome (0,+1,-1) using the *CRAPS-RULES*.

2. Write a function simulate that uses simulate-1 repeatedly to generate a list of all of the dice roll totals in one play of the game.