Before we begin working on Hoon, you should first (1) have Urbit installed and (2) boot a ship that you can use for trying out Hoon examples. Interactive learning is far superior to passive reading.
What is an urbit?
An urbit is an Urbit virtual computer with persistent state that can connect to the Urbit network. (Note the lowercase 'u' here. 'Urbit' is the entire software stack, whereas 'an urbit' is a local instance.) Each urbit is associated with a unique number that plays three distinct roles: (1) it's an address on the Urbit network, (2) it's a cryptographic identity, and (3) it's (in principle) a human memorable name. Normally an urbit's name is represented as a string starting with
~, as in
These may not look like numbers, but they are. Each urbit name is written in a base-256 format, where each 'digit' is a syllable. Imagine your phone number as a pronounceable string which sounds like a name in a foreign language. An ordinary user-level urbit is a 'planet', and it's named by a 32-bit number. The latter is represented as a four-syllable string; e.g., the planet name
~taglux-nidsep is the number 6,095,360.
You can install Urbit on any Mac or Unix machine; if you're just trying out Urbit or creating a development ship, you can follow the steps for creating a development ship here. On Windows, make a virtual Linux machine using VirtualBox or a similar tool.
Once you're finished, you can boot your very own ship. While you can develop in Hoon on your own ship on the live network, we strongly suggest developing on a development ship first.
Once you've created your development ship, let's try a basic command. Type
(add 2 2) at the prompt and hit return. Your screen now shows:
fake: ~zod ames: czar: ~zod on 31337 (localhost only) http: live (insecure, public) on 80 http: live (insecure, loopback) on 12321 > (add 2 2) 4 ~zod:dojo>
You just used a function from the Hoon standard library,
add. Next, quit Urbit with
> (add 2 2) 4 ~zod:dojo> $
Your ship isn't running anymore and you're back at your computer's normal terminal prompt. If your ship is
~zod, then you can restart the ship by typing:
You've already used a standard library function to produce one value, in the dojo. Now that your ship is running again, let's try another. Enter the number
We won't show the
~zod:dojo>prompt from here on out. We'll just show the echoed command along with its result.
> 17 17
You asked dojo to evaluate
17 and it echoed the number back at you. This value is a 'noun'. We'll talk more about nouns in Chapter 1.2, but first let's write a very basic program.
Generators are the most straightforward way to write Hoon programs. They are a concept in Arvo, and involve saving Hoon code in a
.hoon text file. While they aren't strictly part of the Hoon language, we'll be dealing with generators throughout this tutorial.
The simplest type of generator is the naked generator. All naked generators are
gates: functions that take an argument and produce an output. So, to create a generator, all you need to do is write a
gate and put it into a file in the
/home/gen directory of your ship as a
.hoon file. To run a generator named
mygen.hoon, you would type
+myhoon <argument> in your ship's Dojo.
If this doesn't make sense yet, that's okay. In the next lesson, we will walk you through an example
gate that is run as a generator.
Writing code in any language is typically done using a text editor, but common programs like Notepad, Microsoft Word, or OpenOffice Writer are not suitable for programming. You'll want instead a text editor that is specifically designed for writing code. This will assist with things such as colorizing keywords, finding patterns, matching parentheses and brackets, etc.
Below is a complete list of text editors that have support for Hoon syntax highlighting -- an important tool for any programming language. For each of these editors, you'll need to download the editor and then you'll need to install some additional syntax-highlighter package. The process for adding Hoon support differs for every editor. For most newbie-friendly text editors, this is easily accomplished from within the editor itself, and you'll learn how to do so following a newbie tutorial for that editor.
If you are brand new to programming, don't think too much about which editor to use; any of the newbie-friendly options will suit you.
Newbie-friendly text editors
These editors are easy to use for first-time coders.
Atom is free and open-source and runs on all major operating systems. It is available here. A package for Hoon support is maintained by Tlon and may be obtained using the package manager within the editor by searching for
Sublime is closed-source, but may be downloaded for free and there is no enforced time limit for evaluation. It runs on all major operating systems. It is available here.
Visual Studio Code
Visual Studio Code is free and open-source and runs on all major operating systems. It is available here. Hoon support may be acquired in the Extensions menu within the editor by searching for
Advanced text editors
These text editors have a high learning curve and are only recommended for experienced programmers.