From 340e552822343e755331ba749f5e1081fc094955 Mon Sep 17 00:00:00 2001 From: Manu Date: Thu, 11 Jul 2013 23:45:38 +1200 Subject: started on Racket --- racket.html.markdown | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 199 insertions(+) create mode 100644 racket.html.markdown (limited to 'racket.html.markdown') diff --git a/racket.html.markdown b/racket.html.markdown new file mode 100644 index 00000000..27871e50 --- /dev/null +++ b/racket.html.markdown @@ -0,0 +1,199 @@ +TODO: sequences, control flow, macros, objects, modules + +--- +language: racket +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] + + +```racket +; Single line comments start with a semicolon +#| Multiline strings can be written + using three "'s, and are often used + as comments +|# + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 1. Primitive Datatypes and Operators +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + +; You have numbers +1 +9999999999999999999999 ; big integers +3.14 +6.02e+23 +1/2 ; rationals +1+2i ; complex numbers + +; Math is what you would expect +(+ 1 1) ; => 2 +(- 8 1) ; => 7 +(* 10 2) ; => 20 +(quotient 5 2) ; => 2 +(remainder 5 2) ; => 1 +(/ 35 5) ; => 7 +(/ 1 3) ; => 1/3 +(exact->inexact 1/3) ; => 0.3333333333333333 +(+ 1+2i 2-3i) ; => 3-1i + +; Booleans +#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 +(= 2 1) ; => #f + +; Characters +#\A ; => #\A +#\λ ; => #\λ +#\u03BB ; => #\λ + +; 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 + +; Strings can be added too! +(string-append "Hello " "world!") ; => "Hello world!" + +; A string can be treated like a list of characters +(string-ref "Apple" 0) ; => #\A + +; format can be used to format strings: +(format "~a can be ~a" "strings" "formatted") + +; Printing is pretty easy +(printf "I'm Racket. Nice to meet you!\n") + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 2. Variables and Collections +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + +; You need to declare variables before assigning to them. +; a variable name can use any characters except: () [] {} " , ' ` ; # | \ +(define some-var 5) +some-var ; => 5 + +; use set! to reassign +(set! some-var 6) +some-var ; => 6 + +; Accessing a previously unassigned variable is an exception +x ; => x: undefined ... + +; if can be used as an expression + +some_var = a if a > b else b +; If a is greater than b, then a is assigned to some_var. +; Otherwise b is assigned to some_var. + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 3. Collections and Sequences +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + +; Lists are linked-list data structures, vectors are fixed-length arrays. +'(1 2 3) ; a list +#(1 2 3) ; a vector + +; 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 +(append '(1 2) '(3 4)) ; => (1 2 3 4) + +; Use filter, map to interact with collections +(map add1 '(1 2 3)) ; => (2 3 4) +(filter even? '(1 2 3)) ; => (2) + +; Use fold to reduce them +(foldl + 0 '(1 2 3 4)) +; = (+ 1 (+ 2 (+ 3 (+ 4 0))) +; => 10 + +; a sequence is an ordered collection of value +(sequence? '(1 2 3)) ; => #t +(sequence? #(1 2 3)) ; => #t + +;; more sequence stuff here ! + + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 3. Functions +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + +; Use fn to create new functions. A function always returns +; its last statement. +(lambda () "Hello World") ; => # + +; (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" + +; You can shorten this to: +(define (hello-world) "Hello World") + +; 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 +(define hello2 + (case-lambda + [() "Hello World"] + [(name) (string-append "Hello " name)])) +(hello2 "Jake") ; => "Hello Jake" +(hello2) ; => "Hello World" + +; 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 +(define (hello-count name . args) + (format "Hello ~a, you passed ~a extra args" name (length args))) +(hello-count "Finn" 1 2 3) +; => "Hello Finn, you passed 3 extra args" + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 4. Control Flow +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 5. Modules +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 6. Classes +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + + +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; +;; 7. Macros +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; + + +``` + +;; Further Reading + +Still up for more? Try [Quick: An Introduction to Racket with Pictures](http://docs.racket-lang.org/quick/) + -- cgit v1.2.3