Racket language preview

1. A contracted function

#lang line, define/contract, and a format string

horizon-dark

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

atom-one-dark

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

github-dark

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

dracula

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

nord

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

github

#lang racket
;; sum of two numbers with a contract
(define/contract (add a b)
  (-> integer? integer? integer?)
  (+ a b))

(define pi 3.14159)
(displayln (format "~a" (add 1 2)))

2. Structs and pattern matching

struct, match, and square-bracket binding forms

horizon-dark

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

atom-one-dark

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

github-dark

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

dracula

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

nord

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

github

(struct point (x y) #:transparent)

(define (describe p)
  (match p
    [(point 0 0) "origin"]
    [(point x y) (format "(~a, ~a)" x y)]))

(for/list ([p (list (point 0 0) (point 1 2))])
  (describe p))

3. Nested block comments

a comment wrapping an example that has its own comment

horizon-dark

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))

atom-one-dark

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))

github-dark

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))

dracula

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))

nord

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))

github

#| adds two numbers
   #| example: (add 1 2) => 3 |#
|#
(define (add a b)
  (+ a b))