Nexus

Nexus is an LLM-friendly programming language designed for maximum readability, safety, and seamless integration with modern AI-assisted development workflows. It combines a clean, keyword-oriented syntax with a powerful effect system and strict memory management.

Key Philosophy: LLM-Native

Nexus is designed from the ground up to be "AI-friendly":

• Explicit Context: Keyword-terminated blocks (end) provide clear boundaries for LLM context windows.
• Labeled Clarity: Labeled arguments are mandatory at call sites, reducing ambiguity for both humans and AI.
• Predictable Structure: A strict internal A-Normal Form (ANF) ensures the language remains easy to reason about and transform.
• Human-Reviewable: The same properties that help LLMs — explicit block endings, mandatory labels, no implicit behavior — make LLM-generated code straightforward for humans to review and verify.

Key Features

Core Characteristics

• Call-by-Value: Predictable and standard evaluation semantics.
• Null-Free Environment: No null or nil. Optionality is strictly handled via algebraic data types (e.g., Result, Option).
• Mandatory Labeled Arguments: All function call sites must use labels (add(a: 1, b: 2)), ensuring clarity and preventing positional parameter bugs.

Resource & Memory Management (Sigils)

• Syntactic Visibility: Mutability (~) and Linearity (%) are encoded directly into the identifier's name. The state of a resource is visible everywhere it is used.
• Scope-Bound Mutability: Mutable bindings (~) are strictly restricted to the local stack and cannot escape their defining function.
• Linear Types: First-class support for linear resources (%) that must be consumed exactly once, providing compile-time guarantees for file handles, sockets, and other critical resources.

Effects & Concurrency

• Algebraic Effects: A robust effect system using port and handler to decouple logic from side-effect implementation.
• Structured Concurrency: Native conc and task blocks for coordinated and safe parallel execution.
• Wasm-First Design: Built to target the WebAssembly component model for portable and secure deployment.

Usage

Run the REPL:

nexus
Nexus REPL (JIT compiled)
Type :help for available commands, :exit to quit.
>> import { Console, system_handler } form nxlib/stdlib/stdio.nx
>> inject system_handler do
.. Console.print(val: [=[hello]=])
.. end
hello
() : unit

Run a script:

nexus run example.nx

Build a WebAssembly component:

nexus build example.nx            # writes ./main.wasm
nexus build example.nx -o out.wasm  # explicit output path

Run with wasmtime:

# basic component execution
wasmtime run -Scli main.wasm

# when using stdlib/net (HTTP)
wasmtime run -Scli -Shttp -Sinherit-network -Sallow-ip-name-lookup -Stcp main.wasm

See docs/cli.md for the full CLI reference.

Example

import { Console }, * as stdio from nxlib/stdlib/stdio.nx
import { i64_to_string } from nxlib/stdlib/string.nx

let fib = fn (n: i64) -> i64 do
  if n == 0 then
    return 0
  end
  if n == 1 then
    return 1
  end
  let a = fib(n: n - 1)
  let b = fib(n: n - 2)
  return a + b
end

let main = fn () -> unit require { PermConsole } do
  inject stdio.system_handler do
    let v = fib(n: 30)
    let val = i64_to_string(val: v)
    Console.print(val: val)
  end
  return ()
end

Documentation

Document	Description
Syntax	Grammar and EBNF
Types	Type system and inference
Semantics	Evaluation model
Effects	Effect/coeffect system
FFI	Wasm interop
Runtime	Entrypoint and execution
Stdlib	Standard library
CLI	Command-line interface

License

MIT