diff options
Diffstat (limited to 'racket.html.markdown')
| -rw-r--r-- | racket.html.markdown | 111 |
1 files changed, 83 insertions, 28 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index 8cc5ac24..fed3587c 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -11,12 +11,6 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r ```racket #lang racket ; defines the language we are using -; TODO: -; quote -; structs -; control flow (pattern-matching, loops, sequences) - - ; Single line comments start with a semicolon #| Multiline strings can be written using three "'s, and are often used @@ -27,7 +21,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r ;; 1. Primitive Datatypes and Operators ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Numbers +;;; Numbers 9999999999999999999999 ; integers 3.14 ; reals 6.02e+23 @@ -36,8 +30,10 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r ; Function application is written (f x y z ...) ; where f is a function and x, y, z, ... are operands - -; Here are a few arithmetic operators +; 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 (+ 1 1) ; => 2 (- 8 1) ; => 7 (* 10 2) ; => 20 @@ -48,7 +44,7 @@ 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 +;;; Booleans #t ; for true #f ; for false (not #t) ; => #f @@ -57,12 +53,12 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r (= 1 1.0) ; => #t (= 2 1) ; => #f -; Characters +;;; Characters #\A ; => #\A #\λ ; => #\λ #\u03BB ; => #\λ -; Strings are fixed-length array of characters. +;;; Strings are fixed-length array of characters. "Hello, world!" "Benjamin \"Bugsy\" Siegel" ; backslash is an escaping character "λx:(μα.α→α).xx" ; any Unicode character can appear in a string constant @@ -83,7 +79,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r ;; 2. Variables ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; You can create a variable using define -; a variable name can use any characters except: () [] {} " , ' ` ; # | \ +; a variable name can use any character except: ()[]{}",'`;#|\ (define some-var 5) some-var ; => 5 @@ -100,14 +96,29 @@ some-var ; => 6 me) ; => "Bob" ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; 3. Collections +;; 3. Structs and Collections ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +; Structs +(struct dog (name breed age)) +(define my-pet + (dog "lassie" "collie" 5)) +my-pet ; => #<dog> +(dog? my-pet) ; => #t +(dog-name my-pet) ; => "lassie" + +; Pairs +; "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 are linked-list data structures -'(1 2 3) +'(1 2 3) ; => '(1 2 3) ; Vectors are fixed-length arrays -#(1 2 3) +#(1 2 3) ; => '#(1 2 3) ; Use "cons" to add an item to the beginning of a list (cons 4 '(1 2 3)) ; => (4 1 2 3) @@ -167,8 +178,8 @@ m ; => '#hash((b . 2) (a . 1) (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) @@ -210,7 +221,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;; 4. Control Flow ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Conditionals +;;; Conditionals + (if #t ; test expression "this is true" ; then expression "this is false" ; else expression @@ -222,20 +234,61 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) 'yep 'nope) ; => 'yep - ; "cond" chains a series of tests to select a result (cond [(> 2 2) (error "wrong!")] [(< 2 2) (error "wrong again!")] [else 'ok]) ; => 'ok -; Pattern matching +;;; Pattern Matching + +(define (fizzbuzz? n) + (match (list (remainder n 3) (remainder n 5)) + [(list 0 0) 'fizzbuzz] + [(list 0 _) 'fizz] + [(list _ 0) 'buzz] + [_ #f])) + +(fizzbuzz? 15) ; => 'fizzbuzz +(fizzbuzz? 37) ; => #f + +;;; Loops + +(define (loop i) + (when (< i 10) + (printf "i:~a~n" i) + (loop (add1 i)))) + +(loop 5) ; => i:5 i:6 ... -; Loops +(let loop ((i 0)) + (when (< i 10) + (printf "i:~a~n" i) + (loop (add1 i)))) ; => i:0 i:1 ... -; Sequences -; Exceptions +;;; Sequences + +; "for" allows iteration over sequences: +; lists, vectors, strings, sets, hash tables, etc... +(for ([i (in-list '(l i s t))]) + (displayln i)) + +(for ([i (in-vector #(v e c t o r))]) + (displayln i)) + +(for ([i (in-string "string")]) + (displayln i)) + +(for ([i (in-set (set 'x 'y 'z))]) + (displayln i)) + +(for ([(k v) (in-hash (hash 'a 1 'b 2 'c 3 ))]) + (printf "key:~a value:~a ~n" k v)) + + +;;; Exceptions + ; To catch an exception, use the "with-handlers" form ; To throw an exception use "raise" (with-handlers @@ -246,11 +299,12 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 5. Modules ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Modules let you organize code into multiple files and reusable libraries. -(module cake racket/base ;; define a new module 'cake' based on racket/base +; 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 + (provide print-cake) ; function exported by the module (define (print-cake n) (show " ~a " n #\.) @@ -262,7 +316,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) (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 @@ -302,6 +356,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3)) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 7. Macros ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + ; Macros let you extend the syntax of the language (define-syntax-rule (unless test then else) (if test else then)) |