By example

Nyx by example

Worked recipes, in order of difficulty. Each one is a program that compiles and runs with the version in the footer: read it, copy it, change it.

Fundamentals

  1. 01Hello WorldThe simplest Nyx program — printing text to the terminal.
  2. 02VariablesImmutable let, mutable var, basic types, and string interpolation.
  3. 03FunctionsDefining functions with parameters, return types, and default arguments.
  4. 04Control Flowif/else, while loops, for-range, for-in, break and continue.
  5. 05ArraysCreating, indexing, pushing, and iterating over dynamic arrays.
  6. 06MapsKey-value storage with Map.new(), insert, get, has, and key iteration.
  7. 07Stringstrim, length, substring, toUpper, split, contains, and interpolation.
  8. 08StructsDefining data types with fields and attaching methods via impl.
  9. 09EnumsAlgebraic data types with data-carrying variants and exhaustive match.
  10. 10ClosuresFirst-class functions that capture their enclosing environment.
  11. 107continue in forSkip to the next element inside a for loop — over an array and over a range.

Input, output and data

  1. 11File Read & WriteReading and writing files with read_file and write_file.
  2. 12Stdin InputReading user input from the terminal with read_line.
  3. 13CLI ArgumentsAccessing command-line arguments with get_args.
  4. 14Environment VariablesReading env vars with getenv and getenv_default.
  5. 15JSON ParseParsing JSON strings into Maps and Arrays.
  6. 16JSON SerializeConverting data structures back to JSON strings.
  7. 17Regular ExpressionsMatch, extract, and replace with POSIX regex.
  8. 18CSV ParsingSplitting lines and fields to process tabular data.
  9. 19Date and TimeTimestamps, formatted dates, and time measurement.
  10. 20Spawn & ChannelSpawning threads and communicating via channels.
  11. 101File Errors: Two TiersResult when the caller can react, panic when dying is the honest move.
  12. 106JSON: exact numbersjson_stringify re-emits every number exactly as it came in; json_as_float goes through a double and loses the extra zeros.
  13. 116Barcodes and QR codesstd/barcode returns data, not drawings — QR, Code 128 and EAN-13 in pure Nyx, the same program native and in wasm.
  14. 118PDF invoicea letter-size invoice in pure Nyx — right-aligned amounts, a table made of text+line, a PNG logo and a QR, native and in wasm.
  15. 123Build and read a .zip filestd/zip in pure Nyx, no zlib: DEFLATE per entry, CRC-32 checked on read, limits against zip bombs.
  16. 124A purchase ledger as .xlsxstd/xlsx writes a real workbook in pure Nyx: typed cells, merged cells, frozen header, autofilter and thousands separators.
  17. 125Read an .xlsx sheetxlsx_read returns each cell with its type, ISO dates, gaps as empty cells, and default limits against zip bombs.
  18. 133Product photo thumbnailsstd/image decodes at the largest possible reduction, makes several sizes from one decode and flattens transparency onto white.
  19. 138An .xlsx bulk-upload template with dropdownsvalidate_list and validate_list_range restrict a column to allowed values; xlsx_fill marks rejected rows.
  20. 139A PDF that traces a pre-printed formstd/pdf phase 2: line width, gray and color fills, Times and Courier, rotated text, per-page graphic state.
  21. 140Thumbnails of scanned sheetsstd/image on letter-size scans: almost no reduction, so what matters is the build mode.
  22. 143Render a PDF page as an imagestd/pdf_render draws a page of a PDF into an Image on the server, with no external programs; what it cannot draw is either an error or a list you inspect.
  23. 145A large CSV without split() per rowindexOf finds the commas and string_to_float_range parses the number straight from the bytes, without creating a substring per field.
  24. 146A large CSV by columnstry_csv_read parses a CSV in one pass straight into typed columns; a cat column arrives as integer codes plus a dictionary, so grouping is indexing an array.

Types and patterns

  1. 21TraitsDefining shared behavior with trait and impl ... for.
  2. 22Trait BoundsConstraining generics with <T: Display>.
  3. 23Derive CloneAuto-generating Clone, Debug, and other trait impls.
  4. 24Option: Some and NoneHandling optional values with Some and None.
  5. 25Result: Ok and ErrError handling with Ok and Err.
  6. 26Try OperatorShort-circuit error propagation with ?.
  7. 27if letDestructuring enums in conditions with if let.
  8. 28Match GuardsAdding conditions to match arms with if guards.
  9. 29Iterator: map and filterLazy transformations with .iter().filter().map().collect().
  10. 30Iterator: foldReducing a sequence to a single value with fold.
  11. 105An Fn field in a structBind the field to a variable before calling it — the receiver can be a local variable, a by-value parameter or a nested field.
  12. 135Shadowing a name inside a blockA name redeclared in an if, loop, match arm or try is another variable that disappears at the closing brace.
  13. 136defer runs when its block closesdefer fires on leaving the block it is written in — fall-through, return, ?, break or continue — in LIFO order.

Advanced

  1. 31Iterator: enumerate()Getting index and value pairs during iteration.
  2. 32Iterator: take() and skip()Slicing sequences with take and skip.
  3. 33RecursionSolving problems with functions that call themselves.
  4. 34SortingSorting arrays of integers and strings.
  5. 35Error Handlingtry/catch blocks for recovering from runtime errors.
  6. 36Defer and CleanupGuaranteed cleanup with defer { ... } blocks.
  7. 37Sleep and TimersPausing execution and measuring elapsed time.
  8. 38Cryptographic HashingSHA-256, MD5, and HMAC-SHA256 for integrity checking.
  9. 39Random Numbers and UUIDGenerating random numbers and unique identifiers.
  10. 40Thread SpawnRunning functions concurrently with thread_spawn.
  11. 102Template Engine, Flask-StyleInterpolation, #if, #each and partials with std/template.
  12. 109await in the browserAn async fn that waits on the JS host without splitting the flow into callbacks — wasm32-wasi with Asyncify.
  13. 114Offline IndexedDBA catalog and a sales queue that survive an F5 — await over IndexedDB, past localStorage's limit.
  14. 117Web Serial: thermal printer ticketESC/POS bytes straight to a POS printer from wasm32-wasi with await — no system print dialog, cut and cash drawer included.
  15. 121Keep a value across wasm eventsarena_persist copies a String or Array out of the per-event arena so a later event reads it intact — the fix for silently recycled memory.
  16. 128Verify a signed payment webhookstd/rsa checks an RSA-SHA256 signature against the provider's public key: PKCS#1 v1.5 or PSS, true, false or an error.
  17. 131Safe user formulas for payrollstd/expr parses once, evaluates per employee with fixed-point decimals, and reports the position of every error.
  18. 132A PWA talking to a local-network serverLocal Network Access permission plus a timeout on fetch and SSE, so a tablet does not wait minutes on a server that is off.

Networking

  1. 41Base64RFC 4648 encoding/decoding — standard and URL-safe variants.
  2. 42URL EncodePercent-encoding, query strings, and HTML entity escaping.
  3. 43TOML ConfigParsing configuration strings with std/toml.
  4. 44MessagePackBinary serialization: compact, typed, byte-oriented.
  5. 45DNS ResolveConverting hostnames to IP addresses with resolve.
  6. 46TCP ClientConnecting, writing, and reading over raw TCP sockets.
  7. 47TCP ServerListening, accepting, and echoing with tcp_listen.
  8. 48UDP SocketConnectionless datagrams with udp_bind and udp_sendto.
  9. 49HTTP GETHigh-level HTTP client requests with std/http.
  10. 50HTTP POSTPOST requests and custom methods with http_request.
  11. 51HTTP ServerMinimal server with http_serve and request routing.
  12. 52HTTP MiddlewareWeb framework with App, routes, logging, and CORS.
  13. 53WebSocketRFC 6455 framing, parsing, and handshake responses.
  14. 55SQLiteIn-memory SQL database with sqlite_open and sqlite_query.
  15. 56CSV WriteCreating and serializing CSV documents with std/csv.
  16. 103A model written once#[derive(Fields)] and std/postgres: the struct is the only source of truth for the schema.
  17. 104No driver in betweenstd/postgres speaks wire protocol v3 and SCRAM-SHA-256 in pure Nyx — connect, track migrations, and bind parameters without libpq.
  18. 108HTTP: deadline and causeA client that gives up on time and tells WHY it failed: tls, timeout, connection.
  19. 110Server-Sent EventsA channel that doesn't hold a worker: the route runs the full pipeline, then broadcasts to a room.
  20. 113Sending mail with std/smtpMessage, attachment and dot-stuffing built in pure Nyx — STARTTLS on 587 or TLS from the greeting on 465.
  21. 115Repeated form/query keysform_values/query_values recover every value of a repeated key — checkboxes, <select multiple> — where req.form silently keeps only the last.
  22. 119LISTEN/NOTIFY as a live busPostgreSQL fans a notification out to every process's SSE rooms, only if it commits — no Redis in between.
  23. 120Idle keep-alive connectionsworkers is how many requests run at once, not how many connections stay open — an idle tab parks in the event loop and costs no thread.
  24. 122HTTPS to a site with a broken chainHttpOpts.cas_extra adds the missing intermediate certificate for ONE request, without turning verification off.
  25. 126Automatic gzip in std/serveText responses of 1 KiB or more leave compressed when the client sends Accept-Encoding: gzip — no code needed.
  26. 127Body caps and rate limits in std/serveA body cap per route (413) and a request limiter per origin (429 with Retry-After), shared by all workers.
  27. 129HTTPS with a client certificateMutual TLS per request: HttpOpts presents your certificate and key, validated BEFORE connecting.
  28. 130Upload a binary file as multipartmultipart_build and try_http_post_multipart send text fields plus a binary file, and a local server proves the bytes arrive intact.
  29. 134Turn incoming mail into casesstd/imap, std/mime and a UID checkpoint tie a customer's reply back to the quotation thread it answers.
  30. 137OAuth2 for a Gmail or Microsoft 365 mailboxstd/oauth2 builds the PKCE login URL, renews tokens and supports device code — the token imap_auth_xoauth2 and smtp_auth_xoauth2 expect.
  31. 141An email with a text AND an HTML versionsmtp_message_alternative builds multipart/alternative, combines with attachments and does not invent the text for you.
  32. 142Check SPF, DKIM and DMARC before sending mailstd/dns reads TXT and CNAME records and tells NXDOMAIN from NODATA; the checking logic is pure and testable without a network.
  33. 144Forward a streamed response as it arrivestry_http_stream reads another API's response piece by piece and sse_broadcast forwards each event to the browser the moment it lands.

Concurrency

  1. 57MutexProtecting shared state between threads with locks.
  2. 58Channel PatternsMessage passing with buffered channels and sentinels.
  3. 59Worker PoolDispatching tasks to N threads via shared channels.
  4. 60Producer-ConsumerDecoupled pipeline with bounded-channel backpressure.
  5. 61WaitGroupWaiting for multiple threads with wg_add/wg_done/wg_wait.
  6. 62SemaphoreLimiting concurrent access with sem_acquire/sem_release.

Systems

  1. 64Fork & ExecRunning external commands with fork, execvp, and waitpid.
  2. 65PipesConnecting processes with pipe_new and dup2.
  3. 66Signal HandlingRegistering signal callbacks with signal_handle.
  4. 67File WatcherDetecting file changes by polling with stat.
  5. 68Process ControlPID, working directory, terminal detection, and file stat.
  6. 69Raw TerminalCharacter-by-character input with raw_mode_enter.
  7. 70Shebang ScriptRunning Nyx files as executable scripts with #!/usr/bin/env nyx.
  8. 111nyx test --coverageWhich function in src/ no test called — homonyms from different modules never mix when measuring.
  9. 112include_bytesA binary resource that travels inside the executable, read at compile time — no dependence on the file reaching disk.
Nyx, step by stepInstall it, write a first program, set up a project and hand it to an assistant.Open →