Getting Started with Arc

🎮 Want to try Arc without installing? Use the Online Playground!

Installation

Option A: Global Install (recommended)

npm install -g arc-lang

Option B: From Source (for contributors)

git clone https://github.com/kai-builds-ai/arc-lang.git
cd arc-lang/compiler
npm install
cd ..

Requirements: Node.js 18+ and npm.

Editor Support

Install the Arc extension for VS Code for syntax highlighting, diagnostics, hover info, go-to-definition, and completions. Search "Arc Language" in the Extensions panel.

Your First Program

Create a file called hello.arc:

let name = "World"
print("Hello, {name}!")

Run it:

# If installed globally
arc run hello.arc

# If running from source
npx tsx compiler/src/index.ts run hello.arc

Output:

Hello, World!

Using the REPL

Start an interactive session:

# If installed globally
arc repl

# If running from source
npx tsx compiler/src/index.ts repl

Arc REPL v0.1 — Type expressions to evaluate
> 2 + 3
5
> let x = 10
> x * 2
20
> [1, 2, 3] |> map(x => x * 2)
[2, 4, 6]

Language Basics

Variables

let name = "Arc"         # immutable (default)
let mut count = 0        # mutable (opt-in)
count = count + 1

Functions

# Expression body (one-liners)
fn add(a, b) => a + b

# Block body
fn greet(name) {
  let msg = "Hello, {name}!"
  print(msg)
  msg
}

Pipelines

Chain operations left-to-right instead of nesting:

# Instead of: sum(map(filter(data, ...), ...))
data |> filter(x => x > 0) |> map(x => x * 2) |> sum

Pattern Matching

One construct for branching, destructuring, and type checking:

match value {
  0 => "zero",
  n if n < 0 => "negative",
  n => "positive: {n}"
}

Collections

let list = [1, 2, 3, 4, 5]
let evens = [x for x in list if x % 2 == 0]

let map = {name: "Arc", version: 1}

Tool Calls

First-class API calls — no imports, no setup:

let user = @GET "api/users/{id}"
@POST "api/messages" {text: "hello"}

Next Steps

• Language Tour — Complete walkthrough of every feature
• Standard Library Reference — Full stdlib API
• Standard Library Tutorial — Hands-on guide
• Examples — Real-world programs with token comparisons
• FAQ — Common questions answered
• Cheatsheet — Quick reference