diff options
Diffstat (limited to 'racket.html.markdown')
| -rw-r--r-- | racket.html.markdown | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index 7ae9dad0..19b7326d 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -73,7 +73,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r "Hello, world!" "Benjamin \"Bugsy\" Siegel" ; backslash is an escaping character "Foo\tbar\41\x21\u0021\a\r\n" ; includes C escapes, Unicode -"λx:(μα.α→α).xx" ; any Unicode character can appear in a string constant +"λx:(μα.α→α).xx" ; can include Unicode characters ;; Strings can be added too! (string-append "Hello " "world!") ; => "Hello world!" @@ -267,8 +267,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) <-- no `d' ; => "this is true" ;; In conditionals, all non-#f values are treated as true -(member "Groucho" '("Harpo" "Groucho" "Zeppo")) ; => '("Groucho" "Zeppo") -(if (member "Groucho" '("Harpo" "Groucho" "Zeppo")) +(member 'Groucho '(Harpo Groucho Zeppo)) ; => '(Groucho Zeppo) +(if (member 'Groucho '(Harpo Groucho Zeppo)) 'yep 'nope) ; => 'yep @@ -315,7 +315,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) <-- no `d' i) ; => '(2) (for/hash ([i '(1 2 3)]) - (values i (number->string i))) ; => '#hash((1 . "1") (2 . "2") (3 . "3")) + (values i (number->string i))) +; => '#hash((1 . "1") (2 . "2") (3 . "3")) ;; To combine iteration results, use `for/fold' (for/fold ([sum 0]) ([i '(1 2 3 4)]) @@ -371,9 +372,11 @@ vec ; => #(1 2 3 4) ;; 7. Modules ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; Modules let you organize code into multiple files and reusable libraries +;; Modules let you organize code into multiple files and reusable +;; libraries; here we use sub-modules, nested in the whole module that +;; this text makes (starting from the "#lang" line) -(module cake racket/base ; define a new module 'cake' based on racket/base +(module cake racket/base ; define a `cake' module based on racket/base (provide print-cake) ; function exported by the module @@ -404,9 +407,12 @@ vec ; => #(1 2 3 4) ;; Field (define current-size size) ;; Public methods - (define/public (get-size) current-size) - (define/public (grow amt) (set! current-size (+ amt current-size))) - (define/public (eat other-fish) (grow (send other-fish get-size))))) + (define/public (get-size) + current-size) + (define/public (grow amt) + (set! current-size (+ amt current-size))) + (define/public (eat other-fish) + (grow (send other-fish get-size))))) ;; Create an instance of fish% (define charlie @@ -444,7 +450,7 @@ vec ; => #(1 2 3 4) (define a 2) (define b 3) (swap a b) -(printf "tmp = ~a; a = ~a; b = ~a\n" tmp a b) ; tmp is unaffected by swap +(printf "tmp = ~a; a = ~a; b = ~a\n" tmp a b) ; tmp is unaffected ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 10. Contracts @@ -454,7 +460,7 @@ vec ; => #(1 2 3 4) (module bank-account racket (provide (contract-out - [deposit (-> positive? any)] ; amount will always be a positive number + [deposit (-> positive? any)] ; amounts are always positive [balance (-> positive?)])) (define amount 0) @@ -467,7 +473,7 @@ vec ; => #(1 2 3 4) (balance) ; => 5 -;; Any client that attempt to deposit a non-positive amount, will be blamed +;; Clients that attempt to deposit a non-positive amount are blamed ;; (deposit -5) ; => deposit: contract violation ;; expected: positive? ;; given: -5 |