8.15.0.6
Racket Cheat Sheet
Primitives
Numbers
| Literals | integer 1 rational 1/2 complex 1+2i floating 3.14 double 6.02e+23 hex #x29 octal #o32 binary #b010101 |
| Arithmetic | + - * / quotient remainder modulo add1 sub1 max min round floor ceiling sqrt expt exp log sin ... atan |
| Compare | = < <= > >= |
| Bitwise | bitwise-ior bitwise-and bitwise-xor bitwise-not arithmetic-shift integer-length |
| Format | number->string string->number real->decimal-string |
| Test | number? complex? ... exact-nonnegative-integer? ... zero? positive? negative? even? odd? exact? inexact? |
| Misc | random |
| Match Pattern | (? number? n) 42 |
Strings
| Literals | "Racket" quoting "a \" approaches!" unicode "λx:(μα.α→α).xx" |
| Create | make-string string string-append build-string string-join |
| Observe | string-length string-ref substring string-split in-string |
| Modify | string-downcase string-upcase string-trim |
| Test | string? string=? string<=? string-ci<=? |
| Regexp | #rx"a|b" #rx"^c(a|d)+r$" regexp-quote regexp-match regexp-split regexp-replace regexp-replace* |
| Match Pattern | (? string? s) "Banana?" |
Bytes
| Literals | #"rawbytes\0" |
| Create | make-bytes bytes |
| Numbers | integer->integer-bytes real->floating-point-bytes |
| Observe | bytes-length bytes-ref subbytes in-bytes |
| Modify | bytes-set! bytes-copy! bytes-fill! |
| Conversion | bytes->string/utf-8 string->bytes/utf-8 |
| Test | bytes? bytes=? |
| Match Pattern | (? bytes? b) #"0xDEADBEEF" |
Other
| Booleans | #t #f not equal? |
| Characters | #\a #\tab #\λ char? char->integer integer->char char<=? ... char-alphabetic? ... |
| Symbols | 'Racket symbol? eq? string->symbol gensym |
| Boxes | box? box unbox set-box! box-cas! |
| Procedures | procedure? apply compose compose1 keyword-apply procedure-rename procedure-arity curry arity-includes? |
| Void | void? void |
| Undefined | undefined |
Data
Lists
| Create | empty list list* build-list for/list |
| Observe | empty? list? pair? length list-ref member count argmin argmax |
| Use | append reverse map andmap ormap foldr in-list |
| Modify | filter remove ... sort take drop split-at partition remove-duplicates shuffle |
| Match Pattern | (list a b c) (list* a b more) (list top more ...) |
Immutable Hash
| Create | hash hasheq |
| Observe | hash? hash-ref hash-has-key? hash-count in-hash in-hash-keys in-hash-values |
| Modify | hash-set hash-update hash-remove |
Vector
| Create | build-vector vector make-vector list->vector |
| Observe | vector? vector-length vector-ref in-vector |
| Modify | vector-set! vector-fill! vector-copy! vector-map! |
| Match Pattern | (vector x y z) (vector x y calabi–yau ...) |
Streams
| Create | stream stream* empty-stream |
| Observe | stream-empty? stream-first stream-rest in-stream |
Mutable Hash
| Create | make-hash make-hasheq |
| Observe | hash? hash-ref hash-has-key? hash-count in-hash in-hash-keys in-hash-values |
| Modify | hash-set! hash-ref! hash-update! hash-remove! |
Systems
Input/Output
| Formatting | ~a ~v ~s ~e ~r pretty-format |
| Input | read read-bytes peek-byte |
| Output | write write-bytes display displayln pretty-print |
| Ports and Files | with-input-from-file with-output-to-file flush-output file-position make-pipe with-output-to-string with-input-from-string port->bytes port->lines ... |
Files
Miscellaneous
| Time | current-seconds current-inexact-milliseconds date->string date-display-format |
| Command-Line Parsing | command-line |
| FFI | ffi-lib _uint32 ... _fun malloc free |
Networking
Security
| Custodians | make-custodian custodian-shutdown-all current-custodian |
| Sandboxes | make-evaluator make-module-evaluator |
Concurrency
| Threads | thread kill-thread thread-wait make-thread-group |
| Events | sync choice-evt wrap-evt handle-evt alarm-evt ... |
| Channels | make-channel channel-get channel-put |
| Semaphores | make-semaphore semaphore-post semaphore-wait |
| Async Channels | make-async-channel async-channel-get async-channel-put |
Parallelism
| Futures | future touch processor-count make-fsemaphore ... |
| Places | dynamic-place place place-wait place-wait place-channel ... |
| Processes | subprocess system* |
Syntax (Beginner)
Basics
| Modules | (module+ main body ...) (module+ test body ...) (require mod-path) (provide id) |
| S-expressions | quote '(a b c) quasiquote unquote `(1 2 ,(+ 1 2)) |
| Procedure Applications | (fn arg1 arg2) keyword args (fn arg1 #:key arg2) (apply fn arg1 (list arg2)) |
| Procedures | (lambda (x) x) (λ (x) x) (λ (x [opt 1]) (+ x opt)) (λ (x #:req key) (+ x key)) (λ (x #:opt [key 1]) (+ x key)) |
| Binding | (let ([x 1] [y 2]) (+ x y)) (let* ([x 1] [x (+ x 1)]) x) |
| Conditionals | (if (zero? x) 0 (/ 1 x)) (cond [(even? x) 0] [(odd? x) 1] [else "impossible!"]) and or |
| Definitions | (define x 1) (define (f y) (+ x y)) |
| Iteration | for for/list for* |
| Blocks | begin when unless |
| Require Sub-forms | prefix-in only-in except-in rename-in for-syntax for-label ... |
| Provide Sub-forms | all-defined-out all-from-out rename-out ... contract-out |
Structures
| Definition | (struct dillo (weight color)) |
| Create | (define danny (dillo 17.5 'purple)) |
| Observe | (dillo? danny) (dillo-weight danny) (dillo-color danny) |
| Modify | (struct-copy dillo danny ([weight 18.0])) |
| Match Pattern | (dillo w c) |
Pattern Matching
| Basics | (match value [pat body] ...) |
| Definitions | (match-define pat value) |
| Patterns | (quote datum) (list lvp ...) (list-no-order pat ...) (vector lvp ...) (struct-id pat ...) (regexp rx-expr pat) (or pat ...) (and pat ...) (? expr pat ...) |
Syntax (Intermediate)
Basics
| Mutation | set! |
| Exceptions | error with-handlers raise exit |
| Promises | promise? delay force |
| Continuations | let/cc let/ec dynamic-wind call-with-continuation-prompt abort-current-continuation call-with-composable-continuation |
| Parameters | make-parameter parameterize |
| External Files Needed at Runtime | define-runtime-path |
| Continuation Marks | continuation-marks with-continuation-mark continuation-mark-set->list |
| Multiple Values | values let-values define-values call-with-values |
Contracts
| Basics | any/c or/c and/c false/c integer-in vector/c listof list/c ... |
| Functions | -> ->* ->i |
| Application | contract-out recontract-out with-contract define/contract |
Iteration
| Sequences | in-range in-naturals in-list in-vector in-port in-lines in-hash in-hash-keys in-hash-values in-directory in-cycle stop-before stop-after in-stream |
| Generators | generator yield in-generator |
Structures
| Sub-structures | (struct 2d (x y)) (struct 3d 2d (z)) (2d-x (3d 1 2 3)) |
| Mutation | (struct monster (type [hp #:mutable])) (define healie (monster 'slime 10)) (set-monster-hp! healie 0) |
| Transparency | (struct cash ($ ¢) #:transparent) (struct->vector (cash 5 95)) |
| Printing | (struct nickname [n v] #:methods gen:custom-write [(define (write-proc nn p mode) (fprintf p (nickname-n nn)))]) (displayln (nickname "evens" (in-range 0 100 2))) |
| Serialization | (struct txn (who what where) #:prefab) (write (txn "Mustard" "Spatula" "Observatory")) |
Generics
| Definition | define-generics |
| Instantiation | (struct even-set () #:methods gen:set [(define (set-member? st i) (even? i))]) |
Classes
| Definition | interface class* |
| Instantiation | make-object new instantiate |
| Methods | send send/apply send/keyword-apply send* send+ |
| Fields | get-field set-field! |
| Mixins | mixin |
| Traits | trait trait-sum trait-exclude trait-rename ... |
| Contracts | class/c instanceof/c is-a?/c implementation?/c subclass?/c |
Syntactic Abstractions
| Definition | define-syntax define-simple-macro begin-for-syntax for-syntax |
| Templates | syntax syntax/loc with-syntax |
| Parsing ()-Syntax | syntax-parse define-syntax-class pattern |
| Syntax Objects | syntax-source syntax-line ... syntax->datum datum->syntax generate-temporaries format-id |
| Transformers | make-set!-transformer make-rename-transformer local-expand syntax-local-value syntax-local-name syntax-local-lift-expression ... |
| Syntax Parameters | define-syntax-parameter syntax-parameterize syntax-parameter-value |
| Parsing Raw Syntax | lexer parser cfg-parser |
Tools
Packages
| Inspection | raco pkg show |
| Finding | pkgs.racket-lang.org |
| Installing | raco pkg install |
| Updating | raco pkg update |
| Removing | raco pkg remove |
Miscellaneous
| Compiling | raco make program.rkt |
| Testing | raco test program.rkt a-directory |
| Building Executables | raco exe program.rkt |
| Extending DrRacket | drracket:language:simple-module-based-language->module-based-language-mixin |
| Slides | slide standard-fish code |