1.20 Matrix Functions: "matrix.rkt"

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2 | Ht DP/ 2e Teachpacks

▼ | 1 | Ht DP Teachpacks

1.1 | Manipulating Images: "image.rkt"
1.2 | Simulations and Animations: "world.rkt"
1.3 | Converting Temperatures: "convert.rkt"
1.4 | Guessing Numbers: "guess.rkt"
1.5 | Master Minding: "master.rkt"
1.6 | Playing Master Mind: "master-play.rkt"
1.7 | Simple Drawing: "draw.rkt"
1.8 | Hangman: "hangman.rkt"
1.9 | Playing Hangman: "hangman-play.rkt"
1.10 | Managing Control Arrows: "arrow.rkt"
1.11 | Manipulating Simple HTML Documents: "docs.rkt"
1.12 | Working with Files and Directories: "dir.rkt"
1.13 | Graphing Functions: "graphing.rkt"
1.14 | Simple Graphical User Interfaces: "gui.rkt"
1.15 | An Arrow GUI: "arrow-gui.rkt"
1.16 | Controlling an Elevator: "elevator.rkt"
1.17 | Lookup GUI: "lkup-gui.rkt"
1.18 | Guess GUI: "guess-gui.rkt"
1.19 | Queens: "show-queen.rkt"
1.20 | Matrix Functions: "matrix.rkt"

► | 1.20 | Matrix Functions: "matrix.rkt"

1.20.1 | Matrix Snip

On this page:

matrix?
matrix-rows
matrix-cols
rectangle->matrix
matrix->rectangle
make-matrix
build-matrix
matrix-ref
matrix-set
matrix-where?
matrix-render
matrix-minor
1.20.1 Matrix Snip
snip-class

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### 1.20 Matrix Functions: "matrix.rkt"🔗ℹ

(require htdp/matrix) | package: htdp-lib

The experimental teachpack supports matrices and matrix functions. A matrix is just a rectangle of ’objects’. It is displayed as an image, just like the images from Manipulating Images: "image.rkt". Matrices are images and, indeed, scenes in the sense of the Simulations and Animations: "world.rkt".

No educational materials involving matrices exist.

The functions access a matrix in the usual (school-mathematics) manner: row first, column second.

The functions aren’t tuned for efficiency so don’t expect to build programs that process lots of data.

Rectangle A Rectangle (of X) is a non-empty list of lists containing X where all elements of the list are lists of equal (non-zero) length.

> procedure (matrix? o) → boolean?
> o : any/c

determines whether the given object is a matrix?

> procedure (matrix-rows m) → natural-number/c
> m : matrix?

determines how many rows this matrix m has

> procedure (matrix-cols m) → natural-number/c
> m : matrix?

determines ow many columns this matrix m has

> procedure (rectangle->matrix r) → matrix?
> r : Rectangle

creates a matrix from the given Rectangle

> procedure (matrix->rectangle m) → Rectangle
> m : matrix?

creates a rectangle from this matrix m

> procedure (make-matrix n m l) → matrix?
> n : natural-number/c
> m : natural-number/c
> l : (Listof X)

creates an n by m matrix from l

NOTE: make-matrix would consume an optional number of entries, if it were like make-vector

> procedure (build-matrix n m f) → matrix?
> n : natural-number/c
> m : natural-number/c
> | f |  | : |  |
> (-> (and/c natural-number/c (</c m))
> (and/c natural-number/c (</c n))
> any/c)

creates an n by m matrix by applying f to (0 ,0), (0 ,1), ..., ((sub1 m) ,(sub1 n))

> procedure (matrix-ref m i j) → any/c
> m : matrix?
> i : (and/c natural-number/c (</c (matrix-rows m)))
> j : (and/c natural-number/c (</c (matrix-rows m)))

retrieve the item at (i,j) in matrix m

> procedure (matrix-set m i j x) → matrix?
> m : matrix?
> i : (and/c natural-number/c (</c (matrix-rows m)))
> j : (and/c natural-number/c (</c (matrix-rows m)))
> x : any/c

creates a new matrix with x at (i,j) and all other places the same as in m

> procedure (matrix-where? m pred?) → (listof posn?)
> m : matrix?
> pred? : (-> any/c boolean?)

(matrix-where? M P) produces a list of (make-posn i j) such that (P (matrix-ref M i j)) holds

> procedure (matrix-render m) → Rectangle
> m : matrix?

renders this matrix m as a rectangle of strings

> procedure (matrix-minor m i j) → matrix?
> m : matrix?
> i : (and/c natural-number/c (</c (matrix-rows m)))
> j : (and/c natural-number/c (</c (matrix-rows m)))

creates a matrix minor from m at (i,j)

#### 1.20.1 Matrix Snip🔗ℹ

The htdp/matrix teachpack exports the snip-class object to support saving and reading matrix snips.

> value snip-class : (instance/of matrix-snip-class%)

An object to support 2D matrix rendering.
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