Racket Cheatsheet

1549



Sample program

#lang racket/base
(print "Hello, World!")
  • #lang : to define the language you are using
  • print : To display the output in the console
  • ; : To comment a single line
  • ;; : To mark important comments
  • #; : To comment the following s-expression

Data types

DatatypeDescription
Numbersrepresents integers, float and complex numbers
Boolean#t and #f are the two boolean literals
StringsTo represent sequence of characters, double quotes("") are used to represent strings

Variables

Both let and define can be used to define variables.

(let ([id value-expression] ...) body ...+)

(let proc-id ([id init-expression] ...) body ...+)
define id expression

Example

(let ([x 10]) x)

Lists

(list values)

Example

(list 1 2 3 4 5)
List FunctionsUsageDescription
length(length (list 1 2 3 4 5))returns length of the list
list-ref(list-ref (list "a" "b" "c") 0)returns list item at an index
append(append (list "a" "b") (list "c"))to append two lists
reverse(reverse (list "a" "b" "c"))to reverse a list
member(member "g" (list "a" "b" "c"))checks if an element is present in a list

Conditional statements

1. If

(if cond-expr then-expr)

2. If-else

(if cond-expr then-expr else-expr)

Loops

1. For

(for (for-clause ...) body-or-break ... body)

where

for-clause = [id seq-expr] | [(id ...) seq-expr] | #:when guard-expr | #:unless guard-expr | break-clause

body-or-break= body | break-clause

Functions

(def fn functionName args body ...+)

Example

#lang racket/base
(define (square y) (* y y))
(square 5)

Procedures

(lambda (argument-id ...)
  body ...+)