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, timing, signals, LLM integration, actor management, and OTP supervision.

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

| IO | print, println, read | Console input/output | | Int | to_string | Integer conversions | | Timer | sleep | Durable workflow timers | | Signal | wait | Workflow signal suspension | | Inference | ask | AI language model queries (canonical name) | | LLM | ask | Deprecated alias for Inference.ask (RFC 0010) | | Provider | ask | General provider abstraction | | 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 |

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

// IO effects work everywhere
perform IO.print("Hello, World!")
perform IO.println("With a newline")
let input = perform IO.read()

// Actor effects require the runtime
perform Actor.register("my_service")
perform Actor.link(some_actor)

// OTP effects for supervision
let sup = perform Otp.create_supervisor("my_sup", 0)

Adding New Built-in Effects

New built-in operations are registered in the StdLib registry (src/stdlib.rs). The registry is static — it mirrors dispatch sites in vm.rs and runtime/mod.rs and is updated by hand when a new built-in is wired.

Each entry requires:

BuiltinOp {
    name: "Effect.operation",      // Fully-qualified name
    effect: "Effect",              // Effect namespace
    op: "operation",               // Operation within the effect
    signature: "op(args) -> Ret",  // Human-readable signature
    implemented_in: ImplSite::..., // Where it's dispatched
    description: "...",            // One-line behavior description
}

The auto-generated per-effect reference pages are produced from this registry.