1 ;; The first three lines of this file were inserted by DrScheme. They record metadata
2 ;; about the language level of this file in a form that our tools can easily process.
3 #reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname |28.2|) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 Exercise 28.2.1.   Develop a data definition for chessboards.
5 
6 Hint: Use lists. Represent tiles with true and false. A value of true should indicate that a position is available for the placement of a queen; false should indicate that a position is occupied by, or threatened by, a queen.    Solution
7 
8 A row is either
9 1. empty or
10 2. (cons bool ro)
11 where bool is a boolean (true/false), and ro is a row.
12 
13 A chessboard is either
14 1. empty or
15 2. (cons r cb)
16 where r is a row and cb is a chessboard.
17 
18 Specifically, an nxn chessboard is a (listof (listof booleans)) such that the length of each element in the chessboard is the same as the length of the chessboard itself.  That is, the chessboard is square.