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-advanced-reader.ss" "lang")((modname |29.3|) (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 #t #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "arrow.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
4 ;A matrix is a (vectorof (vectorof numbers)).  Specifically, an rxc matrix has a vector-length of r, and each element has a vector-length of c.
5 
6 ;build-matrix : N N (N N -> number) -> matrix
7 ;Given rows and cols, builds a matrix according to f.  f takes in two N's and returns a number (f rows cols).
8 
9 (define (build-matrix rows cols f)
10   (build-vector rows (lambda (r)
11                        (build-vector cols (lambda (c) (f (+ r 1) (+ c 1)))))))
12 
13 (define (transpose a-matrix)
14   (build-matrix (vector-length (vector-ref a-matrix 0))
15                 (vector-length a-matrix)
16                 (lambda (r c) (vector-ref (vector-ref a-matrix (sub1 c)) (sub1 r)))))
17 
18 (define matrix-A (vector (vector 1 0 -1)
19                          (vector 2 0 9)
20                          (vector 1 1 1)))
21 (transpose matrix-A)