# VS Code Extension

To make developing Turing Machines easier, we have developed a Varphi language extension for Visual Studio Code. This extension integrates the Varphi interpreter directly into your editor, providing features like syntax highlighting, error checking, and a fully interactive debugger.

### Installation

You can install the language extension via the [Visual Studio Code marketplace](https://marketplace.visualstudio.com/items?itemName=varphi-lang.varphi).

### Features

#### 1. Syntax Highlighting

The extension provides full syntax highlighting for `.vp` files (the recommended file extension for Varphi). Keywords, states, and tuples are color-coded to improve readability and help you visually structure your transition rules.

#### 2. Live Error Reporting

The extension works in the background to validate your code as you type. It reports errors instantly via the **Problems** panel. Errors are underlined with red squiggles, and hovering over them reveals the specific error message from the compiler.

#### 3. One-Click Execution

You don't need to leave the editor to run your code. The extension adds dedicated **Run** and **Debug** buttons to the editor title bar (top right).

* **Run (Play Icon):** Compiles and executes the current file in a dedicated terminal.
* **Debug (Bug Icon):** Starts an interactive debugging session.

When you click **Run**, the extension opens a dedicated "Varphi" terminal and executes your program, keeping your output separate from other terminal processes.

#### 4. Interactive Debugging (DAP)

The extension communicates with the Varphi Interpreter using the **Debug Adapter Protocol (DAP)**, allowing you to debug Varphi programs just like you would debug other languages.

**Providing Tape Inputs**

When you start a debug session, the extension will prompt you to provide initial values for your tapes via an input box at the top of the screen. You can press `Enter` to leave a tape blank, or `Esc` to finish providing inputs.

**Stepping Through Code**

Once the session starts, you can step through your Turing Machine line-by-line. The editor highlights the active transition rule in yellow, letting you trace exactly which logic is currently being executed.

**Breakpoints**

As with other language extensions, the Varphi extension fully supports breakpoints.

### Configuration

By default, the extension assumes the Varphi Interpreter (`vpi`) is available in your system's `PATH`. If you have installed the interpreter in a custom location, you can configure the path in your VS Code settings:

1. Open Settings (`Ctrl+,`).
2. Search for `Varphi`.
3. Set **Varphi: Interpreter Path** to the location of your executable.

If you prefer editing the setting in JSON, the setting is:

```json
"varphi.interpreterPath": "/path/to/your/vpi"
```

{% hint style="danger" %}
The path to the Varphi Interpreter must not include spaces or quotations.
{% endhint %}


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