The whole reference fits in one sitting. Follow the path in order, then read the example programs.
let, var, numbers, text, and why there are no implicit conversions.if, while, for, ranges, and then expressions.match, and narrowing.try, else, and traps.change, take, and what copies cost.These are the example programs from the Lucid repository. The compiler’s test suite runs them, so they stay current.
Tasks, lists, a loop, is empty, and interpolation.
task greet(name: text) -> text
return "Hello, {name}!"
let people = ["Ada", "Linus"]
for person in people
print greet(person)
if people is empty
print "nobody home"
print "the square root of 2 is {2.0.sqrt()}"A command-line to-do list that saves JSON to a file, with std.args, std.fs, and std.json.
# A small to-do list stored in a JSON file.
# Usage: lucid run todo.lcd add "buy milk"
use std.args
use std.fs
use std.json
type Todo
title: text
done: bool = false
task load(path: text) -> list[Todo]
let raw = fs.read_text(path) else "[]"
return json.parse[list[Todo]](raw) else []
task save(path: text, todos: list[Todo]) -> none or fs.FileError
try fs.write_text(path, json.write(todos))
task show(todos: list[Todo])
for todo in todos
let mark = if todo.done then "x" else " "
print "[{mark}] {todo.title}"
let path = "todos.json"
var todos = load(path)
let command = args.get(0) else "list"
match command
"add" ->
let title = args.get(1) else ""
if title is empty
print "Usage: todo add <title>"
else
todos.push(Todo(title: title))
try save(path, todos)
"list" -> show(todos)
_ -> print "Unknown command: {command}"Threads that share work through a channel and a lock.
# Four threads share a channel of jobs and a lock that holds the total.
task worker(jobs: channel[int], total: lock[int])
while true
let job = jobs.receive()
if job is none
break
total.update(n => n + job * job)
task sum_of_squares(count: int) -> int
let jobs = channel[int](16)
let total = lock(0)
var workers: list[spawned[none]] = []
for i in 0..4
workers.push(spawn worker(jobs, total))
for n in 1..count + 1
jobs.send(n)
jobs.close()
for w in workers
w.wait()
return total.read()
print sum_of_squares(100)An HTTP server with a page and a JSON endpoint, from std.http and std.html.
# A small website with a page and a JSON endpoint. Run it, then open
# http://127.0.0.1:8080 in a browser. A first argument sets another port.
use std.args
use std.html as h
use std.http
type Status
ok: bool
version: text
task home(request: http.Request) -> http.Response
return http.page(h.document("Lucid", [h.h1("Hello from Lucid"), h.a("/status", "Status")]))
task status(request: http.Request) -> http.Response
return http.json(Status(ok: true, version: "0.1.0"))
var app = http.App()
app.get("/", home)
app.get("/status", status)
let port = (args.get(0) else "8080").to_int() else 8080
try app.serve(port)One file holds everything that runs today, sized for an agent’s context window. Give it to the agent with the task, and let it read diagnostics with --json.