diff options
| -rw-r--r-- | racket.html.markdown | 84 |
1 files changed, 42 insertions, 42 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index 25b92f62..fa20bf67 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -7,7 +7,7 @@ contributors: --- -Racket is a general purpose, multi-paradigm programming language in the Lisp/Scheme family. +Racket is a general purpose, multi-paradigm programming language in the Lisp/Scheme family. Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3rac25) or th3rac25 [at] [google's email service] @@ -23,12 +23,12 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r can span multiple lines and... #| they can be nested ! - |# + |# |# ;; S-expression comments discard the following expression #; "this expression will be discarded" "2nd expression" ; => "2nd expression" - + ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 1. Primitive Datatypes and Operators ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; @@ -37,10 +37,10 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r 9999999999999999999999 ; integers 3.14 ; reals 6.02e+23 -1/2 ; rationals -1+2i ; complex numbers +1/2 ; rationals +1+2i ; complex numbers -;; Function application is written (f x y z ...) +;; 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 @@ -56,16 +56,16 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r (exact->inexact 1/3) ; => 0.3333333333333333 (+ 1+2i 2-3i) ; => 3-1i -;;; Booleans -#t ; for true +;;; Booleans +#t ; for true #f ; for false -- any value other than #f is true (not #t) ; => #f (and 0 #f (error "doesn't get here")) ; => #f (or #f 0 (error "doesn't get here")) ; => 0 -;;; Characters +;;; Characters #\A ; => #\A -#\λ ; => #\λ +#\λ ; => #\λ #\u03BB ; => #\λ ;;; Strings are fixed-length array of characters. @@ -111,7 +111,7 @@ some-var ; => 5 ;; Structs (struct dog (name breed age)) -(define my-pet +(define my-pet (dog "lassie" "collie" 5)) my-pet ; => #<dog> (dog? my-pet) ; => #t @@ -173,7 +173,7 @@ my-pet ; => #<dog> (hash-ref m 'd 0) ; => 0 ;; Use "hash-set" to extend a hash table -(define m2 (hash-set m 'd 4)) +(define m2 (hash-set m 'd 4)) m2 ; => '#hash((b . 2) (a . 1) (d . 4) (c . 3)) ;; Remember, these hashes are immutable! @@ -186,7 +186,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; 3. Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; Use lambda to create new functions. +;; Use lambda to create new functions. ;; A function always returns its last statement. (lambda () "Hello World") ; => #<procedure> @@ -201,14 +201,14 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (define (hello-world2) "Hello World") ;; The () is the list of arguments for the function. -(define hello +(define hello (lambda (name) (string-append "Hello " name))) (hello "Steve") ; => "Hello Steve" ;; You can have multi-variadic functions, too (define hello2 - (case-lambda + (case-lambda [() "Hello World"] [(name) (string-append "Hello " name)])) (hello2 "Jake") ; => "Hello Jake" @@ -273,9 +273,9 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) [(list 0 _) 'fizz] [(list _ 0) 'buzz] [_ #f])) - + (fizzbuzz? 15) ; => 'fizzbuzz -(fizzbuzz? 37) ; => #f +(fizzbuzz? 37) ; => #f ;;; Loops @@ -283,9 +283,9 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (define (loop i) (when (< i 10) (printf "i:~a~n" i) - (loop (add1 i)))) + (loop (add1 i)))) -(loop 5) ; => i:5 i:6 ... +(loop 5) ; => i:5 i:6 ... ;; similarly, with a named let (let loop ((i 0)) @@ -310,8 +310,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;;; 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)) @@ -331,8 +331,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; To catch an exception, use the "with-handlers" form ;; To throw an exception use "raise" -(with-handlers - ([(lambda (v) (equal? v "infinity")) +(with-handlers + ([(lambda (v) (equal? v "infinity")) (lambda (exn) +inf.0)]) (raise "infinity")) @@ -342,10 +342,10 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; Use set! to assign a new value to an existing variable (define n 5) -(set! n 6) +(set! n 6) n ; => 6 -;; Many Racket datatypes can be immutable or mutable +;; Many Racket datatypes can be immutable or mutable ;; (Pairs, Lists, Strings, Vectors, Hash Tables, etc...) ;; Use "vector" to create a mutable vector @@ -361,22 +361,22 @@ vec ; => #(1 2 3 4) ;; Modules let you organize code into multiple files and reusable libraries (module cake racket/base ; define a new module 'cake' based on racket/base - + (provide print-cake) ; function exported by the module - + (define (print-cake n) (show " ~a " n #\.) (show " .-~a-. " n #\|) (show " | ~a | " n #\space) (show "---~a---" n #\-)) - - (define (show fmt n ch) ;; internal function + + (define (show fmt n ch) ;; internal function (printf fmt (make-string n ch)) (newline))) ;; Use "require" to import all functions from the module -(require 'cake) -(print-cake 3) +(require 'cake) +(print-cake 3) ; (show "~a" 1 #\A) ; => error, "show" was not exported ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; @@ -385,24 +385,24 @@ vec ; => #(1 2 3 4) ;; Create a class fish% (define fish% - (class object% + (class object% (init size) ; initialization argument - (super-new) ; superclass initialization + (super-new) ; superclass initialization ; Field - (define current-size size) + (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))))) ;; Create an instance of fish% -(define charlie +(define charlie (new fish% [size 10])) ;; Use "send" to call an object's methods (send charlie grow 6) (send charlie get-size) ; => 16 - + ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 9. Macros ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; @@ -421,14 +421,14 @@ 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) + (define tmp x) (set! x y) (set! y tmp))) -(define tmp 1) +(define tmp 1) (define a 2) (define b 3) (swap a b) @@ -444,7 +444,7 @@ vec ; => #(1 2 3 4) (provide (contract-out [deposit (-> positive? any)] ; amount will always be a positive number [balance (-> positive?)])) - + (define amount 0) (define (deposit a) (set! amount (+ amount a))) (define (balance) amount) @@ -456,9 +456,9 @@ 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 +;; (deposit -5) ; => deposit: contract violation ;; expected: positive? -;; given: -5 +;; given: -5 ;; more details.... ``` |