Standard Library Overview

Built-in Effects

Nulang ships with a set of built-in effects wired directly into the VM and runtime. These effects provide core functionality — I/O, collections, strings, timing, HTTP, web serving, actor management, OTP supervision, and AI inference.

Each effect groups related operations accessed via perform Effect.operation(...):

Effect	Operations	Purpose
IO	print, println, read, log, log_error	Console input/output
Int	to_string, to_float, to_hex, to_binary	Integer conversions
Float	to_int, to_string, sin, cos, sqrt, tan, log, exp, log2, log10, pow	Float math and conversions
String	to_int, to_float, length, charAt, from_char, concat, substring	String operations
Array	length, push, new, set, slice	Immutable array operations (value semantics)
Map	new, insert, get, contains, remove, size	Immutable map operations
StrBuilder	new, push, to_string, len, reset	Efficient string building
Debug	inspect	Labeled value inspection
Test	assert, assert_eq, assert_true	Test assertions
Timer	sleep	Durable workflow timers
Time	now	Wall-clock time
Signal	wait	Workflow signal suspension
Random	int	Random integers
FS	read, write, append, exists	File-system access
Env	get	Environment variables
System	arg	Command-line arguments
Process	run	External process execution
Python	import, call, get_attr	Python interop
Http	get, post, serve	HTTP client and server
Web	route, html, text, raw, redirect, serve_static, read_body, param, header, cookie, set_cookie, clear_cookie	Web framework
Realtime	broadcast	Real-time broadcast to connected clients
Inference	ask	AI inference queries (canonical name; LLM.ask remains as a deprecated alias)
Actor	link, unlink, monitor, demonitor, trap_exit, exit, register, unregister, whereis, set_priority	Actor lifecycle management
Otp	create_supervisor, supervise_child, set_template, start_child, terminate_child, child_count	OTP supervision trees
Crdt	increment, decrement, add, remove, set, read	Replicated CRDT state

Nulang-authored Modules

The built-in effects below are runtime/compiler primitives. Nulang also ships higher-level modules written in Nulang itself. Their canonical names, sources, stability tiers, and official package mirrors are generated from the canonical spec/stdlib/v0alpha1.json manifest.

See Standard Library Modules for the generated index.

Implementation Sites

Built-in operations are implemented in one of two places:

• Standalone VM (ImplSite::StandaloneVm) — Operations handled by the VM directly, available in actor-free scripts (e.g., REPL, one-shot --eval).
• Runtime Host (ImplSite::RuntimeHost) — Operations that require the actor runtime, reached through the ActorVmCallbacks trait. These are nil no-ops outside an actor context.

Using Built-in Effects

// Actor-only effects belong inside actor behaviors.
actor Service {
    behavior connect(peer) {
        perform Actor.register("my_service")
        perform Actor.link(peer)
    }
}

actor Peer {
    behavior ping() { unit }
}

fn main() {
    perform IO.print("Hello, World!")
    perform IO.println("With a newline")
    let service = spawn Service {}
    let peer = spawn Peer {}
    service ! connect(peer)

    // OTP supervision is provided by the runtime host.
    let sup = perform Otp.create_supervisor("my_sup", 0)
    0
}

Adding New Built-in Effects

New built-in operations are registered in the StdLib registry in src/stdlib.rs. Nulang-authored module metadata belongs in spec/stdlib/v0alpha1.json; run python3 scripts/generate_stdlib.py after changing it. CI rejects stale generated module metadata and package mirrors. Per-effect reference pages remain auto-generated from the executable StdLib registry.