Questions ?
https://htdp.org/2018-01-06/Book/
https://htdp.org/2018-01-06/Book/part_one.html#(part._ch~3abasic-arithmetic)
Calcul sur des données atomiques
Façon de calculer.
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3aarith-num)
(+ 1 2 3)
(* 4 3 (/ 6 2))
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3aarith-str)
string-append, string-length
(+ (string-length (number->string 42)) 2)
(+ (string-length 42) 1)
Exercice: ajouter un espace entre deux chaînes.
(On fait certains exercices ensemble, on va les refaire en TP.)
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3aarith-images)
(déjà vu la dernière fois)
ouvrir un nouvel onglet, charger 2hdtp/image
montrer que l'on peut couper-coller des images
image-width, image-height
Exercice: nombre de pixels d'une image
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3aarith-bools)
#true, #false
and, or, not
Exercice 7:
(define nice-weather ...)
(define friday ...)
(define good-mood (and nice-weather friday))
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3aboolean-if)
(define x 2)
(1 / x)
(define (divide-or-zero x)
(if (= x 0) 0 (/ 1 x)))
Exécuter, voir les zones noires.
(divide-or-zero 2)
(divide-or-zero 0)
Stepper.
https://htdp.org/2018-01-06/Book/part_one.html#(part._sec~3apredicates)
number?
string?
image?
boolean?
Facultatif:
integer?
exact?
inexact?
Fin des deux heures ?
Exercise 16. Define the function image-area, which counts the number of pixels in a given image. See exercise 6 for ideas.
Exercise 17. Define the function image-classify, which consumes an image and conditionally produces "tall" if the image is taller than wide, "wide" if it is wider than tall, or "square" if its width and height are the same. See exercise 8 for ideas.