Stdlib Reference

The documented surface for core modules: io, fs, os, json, math, bytes, strings, and collections.

I/O, OS, and files

These modules cover the examples that touch the outside world.

io.print, io.println, and io.eprintln write values.
fs.read and fs.write return Result because disk access can fail.
os.args exposes command-line arguments.
os.env returns Option<str> because environment variables can be absent.
os.exit returns ! because the process does not continue.

Math, bytes, and JSON

These modules are small, focused pieces of vocabulary used heavily in examples.

math exposes f64 functions and constants.
bytes.to_hex is useful for binary protocols and diagnostics.
Hex and base64 decoding return Result because input can be malformed.
json.decode::<T> turns external data into typed values and can fail.

String methods

String helpers should make text examples clear while preserving byte-level honesty.

len counts bytes.
chars gives character-level iteration.
split_once returns Option<(str, str)>.
parse::<T> returns Result<T> because text may not represent the requested type.

Collection methods

Collection APIs should reveal ownership and failure modes through their signatures.

Mutation methods require mutable access.
Lookup methods use Option when absence is normal.
Higher-order methods make data transforms readable.
Methods that preserve order should say so when order matters.