urbit/pkg/arvo/gen/brass.hoon
2020-11-21 13:51:20 -08:00

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:: Produce a brass pill
::
:::: /hoon/brass/gen
::
/? 310
/+ pill
::
::::
!:
:- %say
|= $: [now=@da eny=@uvJ bec=beak]
arg=$@(~ [top=path ~])
~
==
::
:: we're creating an event series E whose lifecycle can be computed
:: with the urbit lifecycle formula L, `[2 [0 3] [0 2]]`. that is:
:: if E is the list of events processed by a computer in its life,
:: its final state is S, where S is nock(E L).
::
:: in practice, the first five nouns in E are: two boot formulas,
:: a hoon compiler as a nock formula, the same compiler as source,
:: and the arvo kernel as source.
::
:: after the first five special events, we enter an iterative
:: sequence of regular events which continues for the rest of the
:: computer's life. during this sequence, each state is a function
:: that, passed the next event, produces the next state.
::
:: a regular event is a `[date wire type data]` tuple, where `date` is a
:: 128-bit Urbit date; `wire` is an opaque path which output can
:: match to track causality; `type` is a symbol describing the type
:: of input; and `data` is input data specific to `type`.
::
:: in real life we don't actually run the lifecycle loop,
:: since real life is updated incrementally and also cares
:: about things like output. we couple to the internal
:: structure of the state machine and work directly with
:: the underlying arvo engine.
::
:: this arvo core, which is at `+7` (Lisp `cddr`) of the state
:: function (see its public interface in `sys/arvo`), gives us
:: extra features, like output, which are relevant to running
:: a real-life urbit vm, but don't affect the formal definition.
::
:: so a real-life urbit interpreter is coupled to the shape of
:: the arvo core. it becomes very hard to change this shape.
:: fortunately, it is not a very complex interface.
::
:- %noun
::
:: boot-one: lifecycle formula
::
=+ ^= boot-one
::
:: event 1 is the lifecycle formula which computes the final
:: state from the full event sequence.
::
:: the formal urbit state is always just a gate (function)
:: which, passed the next event, produces the next state.
::
=> [boot-formula=* full-sequence=*]
!= ::
:: first we use the boot formula (event 1) to set up
:: the pair of state function and main sequence. the boot
:: formula peels off the first 5 events
:: to set up the lifecycle loop.
::
=+ [state-gate main-sequence]=.*(full-sequence boot-formula)
::
:: in this lifecycle loop, we replace the state function
:: with its product, called on the next event, until
:: we run out of events.
::
|- ?@ main-sequence
state-gate
%= $
main-sequence +.main-sequence
state-gate .*(state-gate [%9 2 %10 [6 %1 -.main-sequence] %0 1])
==
::
:: boot-two: startup formula
::
=+ ^= boot-two
::
:: event 2 is the startup formula, which verifies the compiler
:: and starts the main lifecycle.
::
=> :* :: event 3: a formula producing the hoon compiler
::
compiler-formula=**
::
:: event 4: hoon compiler source, compiling to event 2
::
compiler-source=*@t
::
:: event 5: arvo kernel source
::
arvo-source=*@t
::
:: events 6..n: main sequence with normal semantics
::
main-sequence=**
==
!= :_ main-sequence
::
:: activate the compiler gate. the product of this formula
:: is smaller than the formula. so you might think we should
:: save the gate itself rather than the formula producing it.
:: but we have to run the formula at runtime, to register jets.
::
:: as always, we have to use raw nock as we have no type.
:: the gate is in fact ++ride.
::
~> %slog.[0 leaf+"1-b"]
=+ ^= compiler-gate
.*(0 compiler-formula)
::
:: compile the compiler source, producing (pair span nock).
:: the compiler ignores its input so we use a trivial span.
::
~> %slog.[0 leaf+"1-c (compiling compiler, wait a few minutes)"]
=+ ^= compiler-tool
.*(compiler-gate [%9 2 %10 [6 %1 [%noun compiler-source]] %0 1])
::
:: switch to the second-generation compiler. we want to be
:: able to generate matching reflection nouns even if the
:: language changes -- the first-generation formula will
:: generate last-generation spans for `!>`, etc.
::
~> %slog.[0 leaf+"1-d"]
=. compiler-gate .*(0 +:compiler-tool)
::
:: get the span (type) of the kernel core, which is the context
:: of the compiler gate. we just compiled the compiler,
:: so we know the span (type) of the compiler gate. its
:: context is at tree address `+>` (ie, `+7` or Lisp `cddr`).
:: we use the compiler again to infer this trivial program.
::
~> %slog.[0 leaf+"1-e"]
=+ ^= kernel-span
-:.*(compiler-gate [%9 2 %10 [6 %1 [-.compiler-tool '+>']] %0 1])
::
:: compile the arvo source against the kernel core.
::
~> %slog.[0 leaf+"1-f"]
=+ ^= kernel-tool
.*(compiler-gate [%9 2 %10 [6 %1 [kernel-span arvo-source]] %0 1])
::
:: create the arvo kernel, whose subject is the kernel core.
::
~> %slog.[0 leaf+"1-g"]
.*(+>:compiler-gate +:kernel-tool)
::
:: sys: root path to boot system, `/~me/[desk]/now/sys`
::
=/ sys=path
?^ arg top.arg
/(scot %p p.bec)/[q.bec]/(scot %da now)/sys
::
:: compiler-source: hoon source file producing compiler, `sys/hoon`
::
=+ compiler-source=.^(@t %cx (welp sys /hoon/hoon))
::
:: compiler-twig: compiler as hoon expression
::
~& %brass-parsing
=+ compiler-twig=(ream compiler-source)
~& %brass-parsed
::
:: compiler-formula: compiler as nock formula
::
~& %brass-compiling
=+ compiler-formula=q:(~(mint ut %noun) %noun compiler-twig)
~& %brass-compiled
::
:: arvo-source: hoon source file producing arvo kernel, `sys/arvo`
::
=+ arvo-source=.^(@t %cx (welp sys /arvo/hoon))
::
:: boot-ova: startup events
::
=+ ^= boot-ova ^- (list *)
:~ boot-one
boot-two
compiler-formula
compiler-source
arvo-source
==
:: a pill is a 3-tuple of event-lists: [boot kernel userspace]
::
=/ bas=path (flop (tail (flop sys)))
:+ boot-ova
:~ :~ //arvo
%what
[/sys/hoon hoon/compiler-source]
[/sys/arvo hoon/arvo-source]
==
(file-ovum2:pill bas)
==
[(file-ovum:pill bas) ~]