Standard library

The standard library is written in Lucid and ships inside the compiler, so a program needs no files beside it. lucid context std.NAME prints the public API of any module, with its doc comments.

Module	Contents	State
prelude	Text, lists, maps, sets, math, core traits, text search, split, trim, case change, list sort, channel, lock	Built
std.fs	Files and directories	Built
std.json	Parse and write, typed by the Json trait	Built
std.env, std.args	Environment variables and command-line words	Built
std.time	Clocks, durations, and UTC dates	Built
std.dom	Browser pages, see WebAssembly	Built
std.net	TCP sockets	Built
std.http	HTTP/1.1 server, and a client with TLS	Built
std.html	HTML building that escapes on render	Built
std.crypto	SHA-256, SHA-512, HMAC, constant-time compare, random bytes, Argon2id	Planned for M8
std.sql	SQLite, with values only through ? marks	Planned for M8

Arguments and environment

use std.args
use std.env

let name = args.get(0) else "world"    # the first word after the program
print "Hello, {name}!"
print env.get("HOME") else "no HOME"

Files

use std.fs

task copy(from: text, to: text) -> none or fs.FileError
    let content = try fs.read_text(from)
    try fs.write_text(to, content)

print fs.exists("notes.txt")
copy("notes.txt", "backup.txt") else none   # ignore a missing file, on purpose

std.fs reads and writes whole files: read_text, write_text, append_text, read_bytes, write_bytes, list_dir, make_dir, remove, and rename. Each gives its result or an fs.FileError, which is NotFound, Denied, NotText, or Failed. exists gives a bool. / works in paths on every system.

JSON

use std.json

type Book
    title: text
    pages: int = 0

let raw = json.write([Book(title: "Dune", pages: 412)])
print raw
let books = json.parse[list[Book]](raw) else []
print books[0].title

Json is derived, with no annotations. A type maps to an object, a choice to "Red" or {"Circle": {"radius": 1.0}}, and a field left out takes its default.

Time

use std.time

let start = time.clock()
time.sleep(time.millis(5))
print time.clock().since(start).to_millis() >= 5
print time.Date(year: 2026, month: 11, day: 6).time().date()

time.now() is the wall clock, and time.clock() only goes forward, for measuring. There are no time zones: dates are UTC.

HTTP

A server routes by method and exact path:

use std.html as h
use std.http

task home(request: http.Request) -> http.Response
    return http.page(h.document("Lucid", [h.h1("Hello from Lucid")]))

var app = http.App()
app.get("/", home)
try app.serve(8080)

app.serve listens on 127.0.0.1 unless given host: "0.0.0.0", runs one thread per connection, and never returns. http.json(value) and http.text(content) build other responses.

The client checks https certificates, with no way to turn the check off, and follows no redirect:

use std.http

let got = try http.get("https://example.com/")
print got.status

HTML

std.html escapes every text and attribute value when it renders, and traps on a script element, an on... attribute, or a javascript: link. So text from a user cannot become markup or code.

Not built yet

There is no console input, no tuples (use a type), and no join, replace, map, filter, sum, min, or max. Write the ones you need as tasks.