Standard library

mu keeps the host builtin surface small and grows capability through mu-written modules.

Three layers

1. Host builtins (Go)
   • A tiny, fixed set like len, append, error, type, inspect, syscall, buf, and dlcall.
2. Prelude helpers (mu)
   • Injected globals like println, panic, test, and exit.
3. Namespaced modules (mu)
   • Import explicitly and call helpers behind a namespace, e.g. strings.split.

Key modules

• sys: file descriptors, stdout/stderr helpers, read/write/open/close
• strings: split/join/trim/replace and string utilities
• time: clocks and sleep helpers
• assert: assertions for tests and scripts
• fp: functional utilities like map/filter/reduce
• json, path, process, sqlite, sockets, text, and more

Example

import "strings"
import "sys"

line := "  hello,mu  "
trimmed := strings.trim(line)
sys.stdout_write(trimmed)

Guidelines

The stdlib stays small, composable, and explicit. New helpers should return errors as values and avoid hidden global state.

See docs/StdlibGuidelines.md for the detailed conventions.

Next steps

• Start with the language tour if you’re new.
• Learn how the VM and native backend work in the runtime guide.
• Explore macros in macros for compile-time helpers.