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Normalize top comments to start with ";;".

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Leave a single ";" for commented expressions and output indications.
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Eli Barzilay 2013-07-16 01:22:11 -04:00
parent 4718ea4e0c
commit 4ad1441e83
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@ -17,7 +17,7 @@ Feedback is appreciated! You can reach me at [@th3rac25](http://twitter.com/th3r
;;; Comments ;;; Comments
; Single line comments start with a semicolon ;; Single line comments start with a semicolon
#| Block comments #| Block comments
can span multiple lines and... 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" #; "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 1/2 ; rationals
1+2i ; complex numbers 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 ;; 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 ;; If you want to create a literal list of data, use ' to stop it from
; being evaluated ;; being evaluated
'(+ 1 2) ; => (+ 1 2) '(+ 1 2) ; => (+ 1 2)
; Now, some arithmetic operations ;; Now, some arithmetic operations
(+ 1 1) ; => 2 (+ 1 1) ; => 2
(- 8 1) ; => 7 (- 8 1) ; => 7
(* 10 2) ; => 20 (* 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 "Benjamin \"Bugsy\" Siegel" ; backslash is an escaping character
"λx:(μα.α→α).xx" ; any Unicode character can appear in a string constant "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!" (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 (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") (format "~a can be ~a" "strings" "formatted")
; Printing is pretty easy ;; Printing is pretty easy
(printf "I'm Racket. Nice to meet you!\n") (printf "I'm Racket. Nice to meet you!\n")
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 2. Variables ;; 2. Variables
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; You can create a variable using define ;; You can create a variable using define
; a variable name can use any character except: ()[]{}",'`;#|\ ;; a variable name can use any character except: ()[]{}",'`;#|\
(define some-var 5) (define some-var 5)
some-var ; => 5 some-var ; => 5
; You can also use unicode characters ;; You can also use unicode characters
(define ⊆ subset?) (define ⊆ subset?)
(⊆ (set 3 2) (set 1 2 3)); => #t (⊆ (set 3 2) (set 1 2 3)); => #t
; Accessing a previously unassigned variable is an exception ;; Accessing a previously unassigned variable is an exception
;x ; => x: undefined ... ; 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"]) (let ([me "Bob"])
"Alice" "Alice"
me) ; => "Bob" me) ; => "Bob"
@ -109,7 +109,7 @@ some-var ; => 5
;; 3. Structs and Collections ;; 3. Structs and Collections
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Structs ;; Structs
(struct dog (name breed age)) (struct dog (name breed age))
(define my-pet (define my-pet
(dog "lassie" "collie" 5)) (dog "lassie" "collie" 5))
@ -118,95 +118,95 @@ my-pet ; => #<dog>
(dog-name my-pet) ; => "lassie" (dog-name my-pet) ; => "lassie"
;;; Pairs (immutable) ;;; Pairs (immutable)
; "cons" constructs pairs, "car" and "cdr" extract the first ;; "cons" constructs pairs, "car" and "cdr" extract the first
; and second elements ;; and second elements
(cons 1 2) ; => '(1 . 2) (cons 1 2) ; => '(1 . 2)
(car (cons 1 2)) ; => 1 (car (cons 1 2)) ; => 1
(cdr (cons 1 2)) ; => 2 (cdr (cons 1 2)) ; => 2
;;; Lists ;;; Lists
; Lists are linked-list data structures ;; Lists are linked-list data structures
(list 1 2 3) ; => '(1 2 3) (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) (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) (append '(1 2) '(3 4)) ; => (1 2 3 4)
;;; Vectors ;;; Vectors
; Vectors are fixed-length arrays ;; Vectors are fixed-length arrays
#(1 2 3) ; => '#(1 2 3) #(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) (vector-append #(1 2 3) #(4 5 6)) ; => #(1 2 3 4 5 6)
;;; Sets ;;; 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) (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) (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) (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) 1) ; => #t
(set-member? (set 1 2 3) 4) ; => #f (set-member? (set 1 2 3) 4) ; => #f
;;; Hashes ;;; 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)) (define m (hash 'a 1 'b 2 'c 3))
; Retrieve a value ;; Retrieve a value
(hash-ref m 'a) ; => 1 (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 ; (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 (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)) (define m2 (hash-set m 'd 4))
m2 ; => '#hash((b . 2) (a . 1) (d . 4) (c . 3)) 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)) 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)) (hash-remove m 'a) ; => '#hash((b . 2) (c . 3))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 3. Functions ;; 3. Functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Use lambda to create new functions. ;; Use lambda to create new functions.
; A function always returns its last statement. ;; A function always returns its last statement.
(lambda () "Hello World") ; => #<procedure> (lambda () "Hello World") ; => #<procedure>
; (You need extra parens to call it) ;; (You need extra parens to call it)
((lambda () "Hello World")) ; => "Hello World" ((lambda () "Hello World")) ; => "Hello World"
; Assign a function to a var ;; Assign a function to a var
(define hello-world (lambda () "Hello World")) (define hello-world (lambda () "Hello World"))
(hello-world) ; => "Hello World" (hello-world) ; => "Hello World"
; You can shorten this to: ;; You can shorten this to:
(define (hello-world2) "Hello World") (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 (define hello
(lambda (name) (lambda (name)
(string-append "Hello " name))) (string-append "Hello " name)))
(hello "Steve") ; => "Hello Steve" (hello "Steve") ; => "Hello Steve"
; You can have multi-variadic functions, too ;; You can have multi-variadic functions, too
(define hello2 (define hello2
(case-lambda (case-lambda
[() "Hello World"] [() "Hello World"]
@ -214,12 +214,12 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
(hello2 "Jake") ; => "Hello Jake" (hello2 "Jake") ; => "Hello Jake"
(hello2) ; => "Hello World" (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) (define (count-args . args)
(format "You passed ~a args: ~a" (length args) args)) (format "You passed ~a args: ~a" (length args) args))
(count-args 1 2 3) ; => "You passed 3 args: (1 2 3)" (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) (define (hello-count name . args)
(format "Hello ~a, you passed ~a extra args" name (length args))) (format "Hello ~a, you passed ~a extra args" name (length args)))
(hello-count "Finn" 1 2 3) (hello-count "Finn" 1 2 3)
@ -229,16 +229,16 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
;; 4. Equality ;; 4. Equality
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; for numbers use "=" ;; for numbers use "="
(= 3 3.0) ; => #t (= 3 3.0) ; => #t
(= 2 1) ; => #f (= 2 1) ; => #f
; for object identity use "eq?" ;; for object identity use "eq?"
(eq? 3 3) ; => #t (eq? 3 3) ; => #t
(eq? 3 3.0) ; => #f (eq? 3 3.0) ; => #f
(eq? (list 3) (list 3)) ; => #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 'a 'b)) ; => #t
(equal? (list 'a 'b) (list 'b 'a)) ; => #f (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 false" ; else expression
) ; => "this is true" ) ; => "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") (member "Groucho" '("Harpo" "Groucho" "Zeppo")) ; => '("Groucho" "Zeppo")
(if (member "Groucho" '("Harpo" "Groucho" "Zeppo")) (if (member "Groucho" '("Harpo" "Groucho" "Zeppo"))
'yep 'yep
'nope) ; => 'yep 'nope) ; => 'yep
; "cond" chains a series of tests to select a result ;; "cond" chains a series of tests to select a result
(cond (cond
[(> 2 2) (error "wrong!")] [(> 2 2) (error "wrong!")]
[(< 2 2) (error "wrong again!")] [(< 2 2) (error "wrong again!")]
@ -279,7 +279,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
;;; Loops ;;; Loops
; looping can be done through recursion ;; looping can be done through recursion
(define (loop i) (define (loop i)
(when (< i 10) (when (< i 10)
(printf "i:~a~n" i) (printf "i:~a~n" i)
@ -287,7 +287,7 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
(loop 5) ; => i:5 i:6 ... (loop 5) ; => i:5 i:6 ...
; similarly, with a named let ;; similarly, with a named let
(let loop ((i 0)) (let loop ((i 0))
(when (< i 10) (when (< i 10)
(printf "i:~a~n" i) (printf "i:~a~n" i)
@ -304,14 +304,14 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
(for/hash ([i '(1 2 3)]) (for/hash ([i '(1 2 3)])
(values i (number->string i))) ; => '#hash((1 . "1") (2 . "2") (3 . "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)]) (for/fold ([sum 0]) ([i '(1 2 3 4)])
(+ sum i)) ; => 10 (+ sum i)) ; => 10
;;; Sequences ;;; Sequences
; "for" allows iteration over sequences: ;; "for" allows iteration over sequences:
; lists, vectors, strings, sets, hash tables, etc... ;; lists, vectors, strings, sets, hash tables, etc...
(for ([i (in-list '(l i s t))]) (for ([i (in-list '(l i s t))])
(displayln i)) (displayln i))
@ -329,8 +329,8 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
;;; Exceptions ;;; Exceptions
; To catch an exception, use the "with-handlers" form ;; To catch an exception, use the "with-handlers" form
; To throw an exception use "raise" ;; To throw an exception use "raise"
(with-handlers (with-handlers
([(lambda (v) (equal? v "infinity")) ([(lambda (v) (equal? v "infinity"))
(lambda (exn) +inf.0)]) (lambda (exn) +inf.0)])
@ -340,17 +340,17 @@ m ; => '#hash((b . 2) (a . 1) (c . 3))
;; 6. Mutation ;; 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) (define n 5)
(set! n 6) (set! n 6)
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...) ;; (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)) (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) (vector-set! vec 0 1)
vec ; => #(1 2 3 4) vec ; => #(1 2 3 4)
@ -358,7 +358,7 @@ vec ; => #(1 2 3 4)
;; 7. Modules ;; 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 (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)) (printf fmt (make-string n ch))
(newline))) (newline)))
; Use "require" to import all functions from the module ;; Use "require" to import all functions from the module
(require 'cake) (require 'cake)
(print-cake 3) (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 ;; 8. Classes and Objects
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Create a class fish% ;; Create a class fish%
(define fish% (define fish%
(class object% (class object%
(init size) ; initialization argument (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 (grow amt) (set! current-size (+ amt current-size)))
(define/public (eat other-fish) (grow (send other-fish get-size))))) (define/public (eat other-fish) (grow (send other-fish get-size)))))
; Create an instance of fish% ;; Create an instance of fish%
(define charlie (define charlie
(new fish% [size 10])) (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 grow 6)
(send charlie get-size) ; => 16 (send charlie get-size) ; => 16
@ -407,9 +407,9 @@ vec ; => #(1 2 3 4)
;; 9. Macros ;; 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 ...) (define-syntax-rule (while condition body ...)
(let loop () (let loop ()
(when condition (when condition
@ -421,7 +421,7 @@ vec ; => #(1 2 3 4)
(displayln i) (displayln i)
(set! i (add1 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) (define-syntax-rule (swap x y)
(begin (begin
(define tmp x) (define tmp x)
@ -438,7 +438,7 @@ vec ; => #(1 2 3 4)
;; 10. Contracts ;; 10. Contracts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Contracts impose constraints on values exported from modules ;; Contracts impose constraints on values exported from modules
(module bank-account racket (module bank-account racket
(provide (contract-out (provide (contract-out
@ -455,14 +455,13 @@ vec ; => #(1 2 3 4)
(balance) ; => 5 (balance) ; => 5
; Any client that attempt to deposit a non-positive amount, will be blamed ;; 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? ;; expected: positive?
; given: -5 ;; given: -5
; more details.... ;; more details....
``` ```
## Further Reading ## Further Reading
Still up for more? Try [Quick: An Introduction to Racket with Pictures](http://docs.racket-lang.org/quick/) Still up for more? Try [Quick: An Introduction to Racket with Pictures](http://docs.racket-lang.org/quick/)