8f2ca31 · urbit.org · git.iko.soy

71The phrase to remember is "a list of moves and our state". Urbit is a

72message passing system, so whenever we want to do something that

73interacts with the rest of the system, we send a message. Thus, a move

74−is arvo's equivalent of a syscall. The first thing that `++poke-noun`

74+is Arvo's equivalent of a syscall. The first thing that `++poke-noun`

75produces is a list of messages, called "moves". In this case, we don't

76actually want the system to do anything, so we produce the empty list,

77`~` (in the `[~ +>.$]` line).

106

107Are there other `++poke`s? Yes. In fact, `noun` and `atom` are just two

108of arbitrarily many "marks". A mark is fundamentally a type definition,

109−but accessible at the arvo level. Each mark is defined in the `/mar`

109+but accessible at the Arvo level. Each mark is defined in the `/mar`

110directory. Some marks have conversion routines to other marks, and some

111have diff, patch, and merge algorithms. None of these are required for a

112mark to exist, however.

201

202Recall that in a `++poke` arm we produce "a list of moves and our

203state". Until now, we've left the list of moves empty, since we haven't

204−wanted to tell arvo to do anything in particular. Now we want to send a

204+wanted to tell Arvo to do anything in particular. Now we want to send a

205message to another urbit. Thus, we produce a list with one element:

206

207 [ost %poke /sending [to-urbit-address %pong] %atom 'howdy']

228

229A duct is stack of causes, again, represented as paths, which are called

230wires. At the bottom of every duct is a unix event, such as a keystroke,

231−network packet, file change, or timer event. When arvo is given this

231+network packet, file change, or timer event. When Arvo is given this

232event, it routes the event to appropriate kernel module for handling.

233

234Sometimes, the module can immediately handle the event and produce any

247an entity finally produces a result, a layer is popped off the duct, and

248the result is passed all the way back down.

249

250−In effect, a duct is an arvo-level call stack. It's worth noting that

250+In effect, a duct is an Arvo-level call stack. It's worth noting that

251while in traditional call stacks a function call happens synchronously

252−and returns exactly once. In arvo, multiple moves can be sent at once,

252+and returns exactly once. In Arvo, multiple moves can be sent at once,

253are evaluated asynchronously, and each one may be responded to zero or

254more times.

255

286that app on that urbit with that data. `[to-urbit-address %pong]` is the

287target urbit and app, `%atom` is the `mark`, and`'howdy'` is the data.

288

289−When arvo receives a `%poke` move, it calls the appropriate `++poke`.

289+When Arvo receives a `%poke` move, it calls the appropriate `++poke`.

290The same mechanism is used for sending messages between apps on the same

291urbit as for sending messages between apps on different urbits.

292