Getting Started

Getting Wren running on your machine is straightforward. Tiny C programs with few dependencies are nice that way. “Wren” encompasses two separate artifacts:

• The virtual machine. This is the core chunk of C that executes Wren source code. It is just a library, not a standalone application. It’s designed to be embedded in a larger host application. It has no dependencies beyond the C standard library. You can use it as a static library, shared library, or simply compile the source into your app.

• The command line executable. Wren also ships with a CLI wrapper around the VM. This gives you a way to run Wren code from the command-line, and also includes modules for talking to the operating system—file IO, networking, stuff like that. It depends on libuv for that functionality.

If you’re on a Unix or Mac and you can rock a command line, it’s just:

$ git clone https://github.com/munificent/wren.git
$ cd wren 
$ make 
$ ./wren

This builds both the VM and the CLI. The release build of the CLI goes right into the repo’s top level directory. Binaries for other configurations are built to bin/. Static and shared libraries for embedding Wren get built in lib/.

For Mac users, there is also an XCode project under util/xcode. For Windows brethren, util/msvc2013 contains a Visual Studio solution. Note that these may not have the exact same build settings as the makefile. The makefile is the “official” way to compile Wren.

If you only want to build the VM, you can do:

$ make vm

This compiles the VM to static and shared libraries.

Interactive mode #

If you just run wren without any arguments, it starts the interpreter in interactive mode. You can type in a line of code, and it immediately executes it. Here’s something to try:

System.print("Hello, world!")

Or a little more exciting:

for (i in 1..10) System.print("Counting up %(i)")

You can exit the interpreter using good old Ctrl-C or Ctrl-D, or just throw your computer to the ground and storm off.

Running scripts #

The standalone interpreter can also load scripts from files and run them. Just pass the name of the script to wren. Create a file named “my_script.wren” in your favorite text editor and paste this into it:

for (yPixel in 0...24) { 
  var y = yPixel / 12 - 1 
  for (xPixel in 0...80) { 
    var x = xPixel / 30 - 2 
    var x0 = x 
    var y0 = y 
    var iter = 0 
    while (iter < 11 && x0 * x0 + y0 * y0 <= 4) { 
      var x1 = (x0 * x0) - (y0 * y0) + x 
      var y1 = 2 * x0 * y0 + y 
      x0 = x1 
      y0 = y1 
      iter = iter + 1 
    } 
    System.write(" .-:;+=xX$& "[iter]) 
  }

  System.print("") 
}

Now run:

$ ./wren my_script.wren

Neat, right? You’re a Wren programmer now! The next step is to learn the language. If you run into bugs, or have ideas or questions, any of the following work:

• Ask on the Wren mailing list.
• Tell me on twitter at @munificentbob.
• File a ticket at the GitHub repo.
• Send a pull request.
• Email me at robert@stuffwithstuff.com.