Examples

Complete programs live in examples/. Each one runs as is from the repository root.

Real-world programs

blog/ — static blog generator

Markdown posts with front matter to an HTML site. Split into modules (site/, md/), finds its content with module.dir, renders pages with """ templates, parses Markdown with regex.

rune run examples/blog/main.rn                    # build the bundled posts into a temp dir
rune run examples/blog/main.rn examples/blog/content site --drafts

todo.rn — task tracker

Tasks with tags, priorities and due dates, kept in a JSON file. Shows fun main with arguments, structs with impl, a Priority enum read back from JSON by name, match on commands, time for dates, and writes the file atomically with fs.rename. Tasks live in $TODO_FILE, or ~/.todo.json.

rune run examples/todo.rn                                  # demo session against a temp file
rune run examples/todo.rn add "pay rent" +home !high due:fri
rune run examples/todo.rn list +home --overdue

validate.rn — config validator

Checks a gateway config against a schema written as data: one struct per rule kind (Str, Duration, List, Tagged…), matched with struct patterns. Every problem is reported with its path (routes[2].auth.type), unknown keys get a “did you mean”, and checks across fields run on the normalized config with ?. and ??. Old config versions are upgraded first by migrations that reshape objects with destructuring and spread.

rune run examples/validate.rn                         # a good, a legacy and a broken config
rune run examples/validate.rn check gateway.json      # exit 1 on any error
rune run examples/validate.rn migrate gateway.json -w # upgrade the file in place
rune run examples/validate.rn normalize gateway.json  # defaults filled, durations in ms

query/ — SQL over CSV

SELECT with joins, WHERE, GROUP BY, HAVING, ORDER BY, LIMIT and EXPLAIN over the CSV files of a directory, split into modules: parser, ast, expr, plan, aggregate, table, output. The parser builds a tree of structs; the planner compiles every expression to a closure over a row array, runs each WHERE conjunct as soon as its tables are there, turns ON a = b into a hash join on a map, and groups with aggregates kept in slots. Errors point at the query with a caret and a “did you mean”. The demo generates 100k orders and times each query.

rune run examples/query/main.rn                              # generate a dataset, run and time queries
rune run examples/query/main.rn "SELECT * FROM users LIMIT 5" -d data -f json
rune run examples/query/main.rn repl -d data                 # one query per line from stdin

log-report.rn — access log report

Per-endpoint latency percentiles, status classes, top clients and slow requests. Reads the log line by line with a stream, groups with map, writes JSON.

rune run examples/log-report.rn                 # generate a sample log and analyze it
rune run examples/log-report.rn access.log -j   # your own log, plus a JSON report

chess.rn — chess engine

Move generation on a 10×12 mailbox board, perft, alpha-beta search with quiescence, a transposition table on Zobrist keys and iterative deepening. Moves are packed into integers with bitwise operators; the position is a struct changed in place by mut self methods make and unmake; table entries record their bound as an enum.

rune run examples/chess.rn                     # perft check, a mate puzzle, self-play
rune run examples/chess.rn perft 4             # leaf nodes per root move
rune run examples/chess.rn go -t 3             # best move from the start position
rune run examples/chess.rn play black -t 2     # play against the engine

calc.rn — calculator

Tokenizer, Pratt parser and evaluator with variables and functions. A good read for structs, an enum of token kinds matched inside struct patterns, match on AST nodes and throw for parse errors.

rune run examples/calc.rn        # demo
rune run examples/calc.rn repl   # read lines from stdin

shop.rn — REST client with auth

A client for the DummyJSON API: logs in, sends a Bearer token, refreshes it on a 401 and retries. http.request with JSON bodies, a Client struct whose mut self methods keep the tokens, a typed ApiError, JWT claims decoded with bytes.fromBase64, a URL encoder over bytes, tables with format.

rune run examples/shop.rn                 # demo user, search "phone"
rune run examples/shop.rn "apple watch"
SHOP_USER=michaelw SHOP_PASS=michaelwpass rune run examples/shop.rn

fetch.rn — HTTP and JSON

Fetches a URL, parses the JSON and handles network errors with try.

rune run examples/fetch.rn

Basics

• fib.rn — Fibonacci numbers, recursion
• bubble-sort.rn — loops and in-place array updates
• linked-list.rn — a linked list built from objects