Monday, July 20, 2015

What I learned about Urbit so far

[Updated, see comment and this Reddit AMA with the Urbit team, that clarifies a lot of issues.]

Urbit is some kind of new operating system design thingy, that is kinda hard to categorize.

Some interesting design points are:
  • Urbit restricts the number of identities in the system to 232. This means Urbit doesn't have enough identities even for currently living humans. In line with the usual obfuscation going on in Urbit, such an identity is called destroyer.
  • Urbit is programmed in a weird programming language called Hoon. Hoon's (only) definition is a 10KLOC file hoon.hoon, written in itself. It uses practically random variable names (such as nail for "parse input", or vase for a "type-value pair"), not to speak of the "nearly 100 ASCII digraph 'runes'". The author acknowledges that the parser is "very intricate".
  • Efficiency-wise, Hoon is impractical as a programming language, so in the real world, the VM will recognize Hoon fragments, and replace them with C code (called jets).
This brings us to the question: why would anybody actually design an OS like that? The best explanation I've seen so far is by Kragen, who writes: