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Diffstat (limited to 'racket.html.markdown')
| -rw-r--r-- | racket.html.markdown | 155 |
1 files changed, 77 insertions, 78 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index 4b72591a..25b92f62 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -17,7 +17,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r ;;; Comments -; Single line comments start with a semicolon +;; Single line comments start with a semicolon #| Block comments can span multiple lines and... @@ -26,7 +26,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r |# |# -; S-expression comments discard the following expression +;; S-expression comments discard the following expression #; "this expression will be discarded" "2nd expression" ; => "2nd expression" ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; @@ -40,12 +40,12 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r 1/2 ; rationals 1+2i ; complex numbers -; Function application is written (f x y z ...) -; where f is a function and x, y, z, ... are operands -; If you want to create a literal list of data, use ' to stop it from -; being evaluated +;; Function application is written (f x y z ...) +;; where f is a function and x, y, z, ... are operands +;; If you want to create a literal list of data, use ' to stop it from +;; being evaluated '(+ 1 2) ; => (+ 1 2) -; Now, some arithmetic operations +;; Now, some arithmetic operations (+ 1 1) ; => 2 (- 8 1) ; => 7 (* 10 2) ; => 20 @@ -73,34 +73,34 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r "Benjamin \"Bugsy\" Siegel" ; backslash is an escaping character "λx:(μα.α→α).xx" ; any Unicode character can appear in a string constant -; Strings can be added too! +;; Strings can be added too! (string-append "Hello " "world!") ; => "Hello world!" -; A string can be treated like a list of characters +;; A string can be treated like a list of characters (string-ref "Apple" 0) ; => #\A -; format can be used to format strings: +;; format can be used to format strings: (format "~a can be ~a" "strings" "formatted") -; Printing is pretty easy +;; Printing is pretty easy (printf "I'm Racket. Nice to meet you!\n") ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 2. Variables ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; You can create a variable using define -; a variable name can use any character except: ()[]{}",'`;#|\ +;; You can create a variable using define +;; a variable name can use any character except: ()[]{}",'`;#|\ (define some-var 5) some-var ; => 5 -; You can also use unicode characters +;; You can also use unicode characters (define ⊆ subset?) (⊆ (set 3 2) (set 1 2 3)); => #t -; Accessing a previously unassigned variable is an exception -;x ; => x: undefined ... +;; Accessing a previously unassigned variable is an exception +; x ; => x: undefined ... -; Local binding: me is bound to "Bob" only within (let ...) +;; Local binding: me is bound to "Bob" only within (let ...) (let ([me "Bob"]) "Alice" me) ; => "Bob" @@ -109,7 +109,7 @@ some-var ; => 5 ;; 3. Structs and Collections ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Structs +;; Structs (struct dog (name breed age)) (define my-pet (dog "lassie" "collie" 5)) @@ -118,95 +118,95 @@ my-pet ; => #<dog> (dog-name my-pet) ; => "lassie" ;;; Pairs (immutable) -; "cons" constructs pairs, "car" and "cdr" extract the first -; and second elements +;; "cons" constructs pairs, "car" and "cdr" extract the first +;; and second elements (cons 1 2) ; => '(1 . 2) (car (cons 1 2)) ; => 1 (cdr (cons 1 2)) ; => 2 ;;; Lists -; Lists are linked-list data structures +;; Lists are linked-list data structures (list 1 2 3) ; => '(1 2 3) -; Use "cons" to add an item to the beginning of a list +;; Use "cons" to add an item to the beginning of a list (cons 4 '(1 2 3)) ; => (4 1 2 3) -; Use "append" to add lists together +;; Use "append" to add lists together (append '(1 2) '(3 4)) ; => (1 2 3 4) ;;; Vectors -; Vectors are fixed-length arrays +;; Vectors are fixed-length arrays #(1 2 3) ; => '#(1 2 3) -; Use "vector-append" to add vectors together +;; Use "vector-append" to add vectors together (vector-append #(1 2 3) #(4 5 6)) ; => #(1 2 3 4 5 6) ;;; Sets -; create a set from a list +;; create a set from a list (list->set '(1 2 3 1 2 3 3 2 1 3 2 1)) ; => (set 1 2 3) -; Add a member with "set-add" +;; Add a member with "set-add" (set-add (set 1 2 3) 4); => (set 1 2 3 4) -; Remove one with "set-remove" +;; Remove one with "set-remove" (set-remove (set 1 2 3) 1) ; => (set 2 3) -; Test for existence with "set-member?" +;; Test for existence with "set-member?" (set-member? (set 1 2 3) 1) ; => #t (set-member? (set 1 2 3) 4) ; => #f ;;; Hashes -; Create an immutable hash table (There are also mutables ones) +;; Create an immutable hash table (There are also mutables ones) (define m (hash 'a 1 'b 2 'c 3)) -; Retrieve a value +;; Retrieve a value (hash-ref m 'a) ; => 1 -; Retrieving a non-present value is an exception +;; Retrieving a non-present value is an exception ; (hash-ref m 'd) => no value found -; You can provide a default value for missing keys +;; You can provide a default value for missing keys (hash-ref m 'd 0) ; => 0 -; Use "hash-set" to extend a hash table +;; Use "hash-set" to extend a hash table (define m2 (hash-set m 'd 4)) m2 ; => '#hash((b . 2) (a . 1) (d . 4) (c . 3)) -; Remember, these hashes are immutable! +;; Remember, these hashes are immutable! m ; => '#hash((b . 2) (a . 1) (c . 3)) -; Use "hash-remove" to remove keys +;; Use "hash-remove" to remove keys (hash-remove m 'a) ; => '#hash((b . 2) (c . 3)) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 3. Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Use lambda to create new functions. -; A function always returns its last statement. +;; Use lambda to create new functions. +;; A function always returns its last statement. (lambda () "Hello World") ; => #<procedure> -; (You need extra parens to call it) +;; (You need extra parens to call it) ((lambda () "Hello World")) ; => "Hello World" -; Assign a function to a var +;; Assign a function to a var (define hello-world (lambda () "Hello World")) (hello-world) ; => "Hello World" -; You can shorten this to: +;; You can shorten this to: (define (hello-world2) "Hello World") -; The () is the list of arguments for the function. +;; The () is the list of arguments for the function. (define hello (lambda (name) (string-append "Hello " name))) (hello "Steve") ; => "Hello Steve" -; You can have multi-variadic functions, too +;; You can have multi-variadic functions, too (define hello2 (case-lambda [() "Hello World"] @@ -214,12 +214,12 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (hello2 "Jake") ; => "Hello Jake" (hello2) ; => "Hello World" -; Functions can pack extra arguments up in a list +;; Functions can pack extra arguments up in a list (define (count-args . args) (format "You passed ~a args: ~a" (length args) args)) (count-args 1 2 3) ; => "You passed 3 args: (1 2 3)" -; You can mix regular and packed arguments +;; You can mix regular and packed arguments (define (hello-count name . args) (format "Hello ~a, you passed ~a extra args" name (length args))) (hello-count "Finn" 1 2 3) @@ -229,16 +229,16 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; 4. Equality ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; for numbers use "=" +;; for numbers use "=" (= 3 3.0) ; => #t (= 2 1) ; => #f -; for object identity use "eq?" +;; for object identity use "eq?" (eq? 3 3) ; => #t (eq? 3 3.0) ; => #f (eq? (list 3) (list 3)) ; => #f -; for collections use "equal?" +;; for collections use "equal?" (equal? (list 'a 'b) (list 'a 'b)) ; => #t (equal? (list 'a 'b) (list 'b 'a)) ; => #f @@ -253,13 +253,13 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) "this is false" ; else expression ) ; => "this is true" -; In conditionals, all non-#f values are treated as true +;; In conditionals, all non-#f values are treated as true (member "Groucho" '("Harpo" "Groucho" "Zeppo")) ; => '("Groucho" "Zeppo") (if (member "Groucho" '("Harpo" "Groucho" "Zeppo")) 'yep 'nope) ; => 'yep -; "cond" chains a series of tests to select a result +;; "cond" chains a series of tests to select a result (cond [(> 2 2) (error "wrong!")] [(< 2 2) (error "wrong again!")] @@ -279,7 +279,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;;; Loops -; looping can be done through recursion +;; looping can be done through recursion (define (loop i) (when (< i 10) (printf "i:~a~n" i) @@ -287,7 +287,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (loop 5) ; => i:5 i:6 ... -; similarly, with a named let +;; similarly, with a named let (let loop ((i 0)) (when (< i 10) (printf "i:~a~n" i) @@ -304,14 +304,14 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (for/hash ([i '(1 2 3)]) (values i (number->string i))) ; => '#hash((1 . "1") (2 . "2") (3 . "3")) -; To combine iteration results, use "for/fold" +;; To combine iteration results, use "for/fold" (for/fold ([sum 0]) ([i '(1 2 3 4)]) (+ sum i)) ; => 10 ;;; Sequences -; "for" allows iteration over sequences: -; lists, vectors, strings, sets, hash tables, etc... +;; "for" allows iteration over sequences: +;; lists, vectors, strings, sets, hash tables, etc... (for ([i (in-list '(l i s t))]) (displayln i)) @@ -329,8 +329,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;;; Exceptions -; To catch an exception, use the "with-handlers" form -; To throw an exception use "raise" +;; To catch an exception, use the "with-handlers" form +;; To throw an exception use "raise" (with-handlers ([(lambda (v) (equal? v "infinity")) (lambda (exn) +inf.0)]) @@ -340,17 +340,17 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; 6. Mutation ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Use set! to assign a new value to an existing variable +;; Use set! to assign a new value to an existing variable (define n 5) (set! n 6) n ; => 6 -; Many Racket datatypes can be immutable or mutable -; (Pairs, Lists, Strings, Vectors, Hash Tables, etc...) +;; Many Racket datatypes can be immutable or mutable +;; (Pairs, Lists, Strings, Vectors, Hash Tables, etc...) -; Use "vector" to create a mutable vector +;; Use "vector" to create a mutable vector (define vec (vector 2 2 3 4)) -; Use vector-set! to update a slot +;; Use vector-set! to update a slot (vector-set! vec 0 1) vec ; => #(1 2 3 4) @@ -358,7 +358,7 @@ 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 (module cake racket/base ; define a new module 'cake' based on racket/base @@ -374,16 +374,16 @@ vec ; => #(1 2 3 4) (printf fmt (make-string n ch)) (newline))) -; Use "require" to import all functions from the module +;; Use "require" to import all functions from the module (require 'cake) (print-cake 3) -;(show "~a" 1 #\A) ; => error, "show" was not exported +; (show "~a" 1 #\A) ; => error, "show" was not exported ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 8. Classes and Objects ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Create a class fish% +;; Create a class fish% (define fish% (class object% (init size) ; initialization argument @@ -395,11 +395,11 @@ vec ; => #(1 2 3 4) (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% +;; Create an instance of fish% (define charlie (new fish% [size 10])) -; Use "send" to call an object's methods +;; Use "send" to call an object's methods (send charlie grow 6) (send charlie get-size) ; => 16 @@ -407,9 +407,9 @@ vec ; => #(1 2 3 4) ;; 9. Macros ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Macros let you extend the syntax of the language +;; Macros let you extend the syntax of the language -; Let's add a while loop +;; Let's add a while loop (define-syntax-rule (while condition body ...) (let loop () (when condition @@ -421,7 +421,7 @@ vec ; => #(1 2 3 4) (displayln i) (set! i (add1 i)))) -; Macros are hygienic, you cannot clobber existing variables! +;; Macros are hygienic, you cannot clobber existing variables! (define-syntax-rule (swap x y) (begin (define tmp x) @@ -438,7 +438,7 @@ vec ; => #(1 2 3 4) ;; 10. Contracts ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Contracts impose constraints on values exported from modules +;; Contracts impose constraints on values exported from modules (module bank-account racket (provide (contract-out @@ -455,14 +455,13 @@ vec ; => #(1 2 3 4) (balance) ; => 5 -; Any client that attempt to deposit a non-positive amount, will be blamed -; (deposit -5) ; => deposit: contract violation -; expected: positive? -; given: -5 -; more details.... +;; Any client that attempt to deposit a non-positive amount, will be blamed +;; (deposit -5) ; => deposit: contract violation +;; expected: positive? +;; given: -5 +;; more details.... ``` ## Further Reading Still up for more? Try [Quick: An Introduction to Racket with Pictures](http://docs.racket-lang.org/quick/) - |