1. Racket Last Structs, Lambda, Module
CSC270 Pepper
major portions credited to

2. Structs
; Define structure: (struct student (name gpa age)) ; structure type definition: (define s1 (student "amy jones" )) ; use of one part of struct variable: (student-name s1) ; check type : (student? s1 )

3. Shape Structures (struct circle (radius)) (define c1 (circle 10))
(struct rect (length width))
(define r1 (rect 10 20))
(define r2 (rect 11 12))

4. Area Functions
(define (area a-shape) (cond [(rect? a-shape) (* (rect-length a-shape) (rect-width a-shape))] [ (circle? a-shape) (* (expt (circle-radius a-shape) 2)pi)])) (area c1) (area r1) (area (rect 10 30)

5. Functions Passing in Functions
First class functions
(define (square num) (* num num))
(define (pow3 num) (* num num num))
(define (calc numberfunc) (numberfunc 10))
(calc square);
(calc pow3);
Plus Remember map:
(define (add3 x) (+ x 3))
(map add3 '(1 2 3))

6. Lambda Functions (lambda () "Hello")
; surround with parentheses to call
(( lambda () "Hello"))
; function with a parm
(lambda (num) (+ num 3))
((lambda (num) (+ num 3)) 5)
All functions have an implied lambda

7. Define and Lambda ; assign a lambda function to a symbol
(define Lhello-world ( lambda() "Hello"))
; same as (define (Lhello-world) "hello")
(Lhello-world)
(define Ladd3 ( lambda (num) (+ num 3)))
; second same as (define (Ladd3 num) (+ num 3))
(Ladd3 5)
; see how all functions have an implied lambda?

8. Functions Passing in Functions
(define (triangleperm a b c) (+ a b c)) (define (equiTriangle a) (triangleperm a a a)); (calc equiTriangle); Or instead of defining equiTriangle, create an anonymous function: (calc (lambda (x) (triangleperm x x x)))

9. Map Lambda functions Define a function
Use it in map
(define (add3 x) (+ x 3))
(map add3 '(1 2 3))
Define that same function anonymously
(map (lambda (i) (+ i 3)) '(1 2 3))

10. Adding New Commands EASY (define-syntax-rule (swap! x y)
(let ([temp x]) (set! x y) (set! y temp)))
(define x 3)
(define y 4)
(swap! x y) x y

11. Modules
create it with (module moduleName itsBase) example (module cake racket/base)
list functions the importer can use with (provide functionName) example (provide bake-cake)
no indication of parameters needed
To import a module : (require ModuleName) example (require picturing-programs)

12. Important Concepts Define data in parts : structure
Functions can take in functions as parms
On the fly functions give flexibility