Skip to content

Starting Jac, Variables and Types#

The first step is setting up your development environment. We'll cover how to install Jac, configure your code editor, and write and run your first program.

To get started, you will need Python 3.12 or newer. While you can use any text editor, we recommend using VS Code with the official Jac extension for the best experience, as it provides helpful features like syntax highlighting and error checking.

Installation and IDE Setup#

System Requirements#

  • Python 3.12 or higher
  • pip package manager
  • 4GB RAM minimum (8GB recommended)
  • 500MB storage for Jac and dependencies

Installing Jac#

We recommend installing Jac in a virtual environment to keep your project's dependencies separate from your system's Python packages.

Quick Install via pip#

# Install Jac from PyPI
$ pip install jaclang

# Verify installation
$ jac --version

For project isolation, consider using a virtual environment:

Linux/MacOS

# Create virtual environment
$ python -m venv jac-env

# Activate it (Linux/Mac)
$ source jac-env/bin/activate

# Install Jac
$ pip install jaclang

Windows 

# Create virtual environment
python -m venv jac-env

# Activate it (Windows)
jac-env\Scripts\activate

# Install Jac
pip install jaclang

VS Code Extension#

For the best development experience, install the Jac VS Code extension:

  1. Open VS Code
  2. Go to Extensions (Ctrl+Shift+X)
  3. Search for "Jac"
  4. Install the official Jac extension

Alternatively, visit the VS Code marketplace directly.

The extension provides:

  • Color-coding for Jac's syntax to make it easier to read.
  • Automatic detection of errors in your code.
  • Tools for formatting your code consistently.
  • Visualizations of your graph data structures.

Basic CLI Commands#

Jac provides a simple command-line interface (CLI) for running scripts and managing projects. This cli provides developers the ability to either run scripts locally for testing or even serve them as web applications. Here are the most common commands: 

# Run a Jac file
$ jac run filename.jac

# Get help
$ jac --help

# Serve as web application (advanced)
$ jac serve filename.jac

Hello World in Jac#

Let's write and run your first Jac program. 1. Create a new file named hello.jac. 2. Add the following code to the file:

# hello.jac
with entry {
    print("Hello, Jac World!");
}

Run the program from your terminal. 

$ jac run hello.jac

You will see the following output:


Hello, Jac World!

If you see this information, you have installed Jac successfully! You're ready to write your first program.

Entry Blocks and Basic Execution#

The with entry block is Jac's equivalent to Python's if __name__ == "__main__": - it defines where program execution begins. Any code inside this block is executed when you run the file.

Single Entry Blocks#

# Entry block - program starts here
with entry {
    print("Hello single entry block!");
}

Multiple Entry Blocks#

Jac allows multiple entry blocks that execute in order:

# First entry block
with entry {
    print("Hello first entry block!");
}

# Second entry block
with entry {
    print("Hello second entry block!");
}

# Third entry block
with entry {
    print("Hello third entry block!");
}

You have now successfully set up your development environment, written your first Jac program, and learned how the with entry block works.

From here, you can continue your journey in a way that best suits your learning style. You can go through the Learn Jac Language section for in-depth knowledge or learn using our hands-on Examples.

Next Steps#