►How to Design Programs Teachpacks
▼1 Ht  DP Teachpacks
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
  top  ← prev  up  next → 

1.20 Matrix Functions: "matrix.rkt"

 (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)

  top  ← prev  up  next →