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| -rw-r--r-- | racket.html.markdown | 130 |
1 files changed, 99 insertions, 31 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index db85edb0..0d75e8a2 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -1,38 +1,43 @@ -TODO: sequences, control flow, macros, objects, modules - --- language: racket -author: Th3rac25 +author: th3rac25 --- Racket is a general purpose, multi-paradigm programming language in the Lisp/Scheme family. -Feedback would be highly appreciated! You can reach me at [@th3rac25](http://twitter.com/th3rac25) or th3rac25 [at] [google's email service] +Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3rac25) or th3rac25 [at] [google's email service] ```racket +#lang racket ; defines the language we are using + +; TODO: +; quote +; collections (set, hash) +; structs +; control flow (pattern-matching, loops, sequences) +; objects + + ; Single line comments start with a semicolon #| Multiline strings can be written using three "'s, and are often used as comments |# - -#lang racket ; defines the language we are using - ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 1. Primitive Datatypes and Operators ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; You have numbers -1 9999999999999999999999 ; big integers -3.14 +3.14 ; reals 6.02e+23 -1/2 ; rationals -1+2i ; complex numbers +1/2 ; rationals +1+2i ; complex numbers -; Math is what you would expect +; Operators are functions, functions applications are written +; (f x y z ...) where f is a function and x, y, z, ... are operands (+ 1 1) ; => 2 (- 8 1) ; => 7 (* 10 2) ; => 20 @@ -47,7 +52,6 @@ Feedback would be highly appreciated! You can reach me at [@th3rac25](http://twi #t ; for true #f ; for false (not #t) ; => #f -; In conditionals, all non-#f values are treated as true ; Equality for numbers is = (= 1 1.0) ; => #t @@ -76,23 +80,27 @@ Feedback would be highly appreciated! You can reach me at [@th3rac25](http://twi (printf "I'm Racket. Nice to meet you!\n") ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; 2. Variables and Collections +;; 2. Variables ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; - -; You need to declare variables before assigning to them. +; You can create a variable using define ; a variable name can use any characters except: () [] {} " , ' ` ; # | \ (define some-var 5) some-var ; => 5 -; use set! to reassign +; Use set! to assign a new value to an existing variable (set! some-var 6) some-var ; => 6 ; Accessing a previously unassigned variable is an exception -x ; => x: undefined ... +;x ; => x: undefined ... + +; Local binding: me is bound to "Bob" only within (let ...) +(let ([me "Bob"]) + "Alice" + me) ; => "Bob" ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -;; 3. Collections and Sequences +;; 3. Collections ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Lists are linked-list data structures, vectors are fixed-length arrays. @@ -114,28 +122,23 @@ x ; => x: undefined ... ; = (+ 1 (+ 2 (+ 3 (+ 4 0))) ; => 10 -; a sequence is an ordered collection of value -(sequence? '(1 2 3)) ; => #t -(sequence? #(1 2 3)) ; => #t +; Set + -;; more sequence stuff here ! +; Hash ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 3. Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -; Use fn to create new functions. A function always returns +; Use lambda to create new functions. A function always returns ; its last statement. (lambda () "Hello World") ; => #<procedure> ; (You need extra parens to call it) ((lambda () "Hello World")) ; => "Hello World" -; You can create a variable using define -(define x 1) -x ; => 1 - ; Assign a function to a var (define hello-world (lambda () "Hello World")) (hello-world) ; => "Hello World" @@ -171,12 +174,61 @@ x ; => 1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 4. Control Flow ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +; Conditionals +(if #t ; test expression + "this is true" ; then expression + "this is false" ; else expression + ) ; => "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")) + 'yep + 'nope) ; => 'yep + + +; Cond chains a series of test to select a result +(cond + [(> 2 2) (error "wrong!")] + [(< 2 2) (error "wrong again!")] + [else 'ok]) ; => 'ok +; Pattern matching + +; Loops + +; Sequences + +; Exceptions +; 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)]) + (raise "infinity")) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 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 + + (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 + (printf fmt (make-string n ch)) + (newline))) + +(require 'cake) ;; import all 'cake' functions +(print-cake 3) +;(show "~a" 1 #\A) ; => this is an error ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 6. Classes @@ -186,8 +238,24 @@ x ; => 1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 7. Macros ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; - - +; Macros let you extend the syntax of the language +(define-syntax-rule (unless test then else) + (if test else then)) + +(unless (even? 10) "odd" "even") ; => "even" + +; Macros are hygienic, there is no risk to clobber existing variables! +(define-syntax-rule (swap x y) + (begin + (define tmp x) + (set! x y) + (set! y tmp))) + +(define tmp 1) +(define a 2) +(define b 3) +(swap a b) +(printf "tmp = ~a; a = ~a; b = ~a" tmp a b) ; tmp is unaffected by swap ``` ;; Further Reading |