mirror of
https://github.com/ilyakooo0/urbit.git
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168 lines
4.0 KiB
Plaintext
168 lines
4.0 KiB
Plaintext
|%
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+$ card card:agent:gall
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+$ input
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$% [%poke =cage]
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[%sign =wire =sign-arvo]
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[%agent =wire =sign:agent:gall]
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[%watch =path]
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==
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+$ strand-input [=bowl in=(unit input)]
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+$ tid @tatid
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+$ bowl
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$: our=ship
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src=ship
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tid=tid
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mom=(unit tid)
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wex=boat:gall
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sup=bitt:gall
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eny=@uvJ
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now=@da
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byk=beak
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==
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::
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:: cards: cards to send immediately. These will go out even if a
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:: later stage of the computation fails, so they shouldn't have
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:: any semantic effect on the rest of the system.
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:: Alternately, they may record an entry in contracts with
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:: enough information to undo the effect if the computation
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:: fails.
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:: wait: don't move on, stay here. The next sign should come back
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:: to this same callback.
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:: skip: didn't expect this input; drop it down to be handled
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:: elsewhere
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:: cont: continue computation with new callback.
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:: fail: abort computation; don't send effects
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:: done: finish computation; send effects
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::
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++ strand-output-raw
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|* a=mold
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$~ [~ %done *a]
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$: cards=(list card)
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$= next
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$% [%wait ~]
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[%skip ~]
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[%cont self=(strand-form-raw a)]
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[%fail err=(pair term tang)]
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[%done value=a]
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==
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==
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::
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++ strand-form-raw
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|* a=mold
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$-(strand-input (strand-output-raw a))
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::
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:: Abort strand computation with error message
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::
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++ strand-fail
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|= err=(pair term tang)
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|= strand-input
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[~ %fail err]
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::
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:: Asynchronous transcaction monad.
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::
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:: Combo of four monads:
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:: - Reader on input
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:: - Writer on card
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:: - Continuation
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:: - Exception
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::
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++ strand
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|* a=mold
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|%
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++ output (strand-output-raw a)
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::
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:: Type of an strand computation.
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::
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++ form (strand-form-raw a)
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::
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:: Monadic pure. Identity computation for bind.
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::
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++ pure
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|= arg=a
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^- form
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|= strand-input
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[~ %done arg]
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::
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:: Monadic bind. Combines two computations, associatively.
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::
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++ bind
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|* b=mold
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|= [m-b=(strand-form-raw b) fun=$-(b form)]
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^- form
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|= input=strand-input
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=/ b-res=(strand-output-raw b)
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(m-b input)
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^- output
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:- cards.b-res
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?- -.next.b-res
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%wait [%wait ~]
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%skip [%skip ~]
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%cont [%cont ..$(m-b self.next.b-res)]
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%fail [%fail err.next.b-res]
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%done [%cont (fun value.next.b-res)]
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==
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::
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:: The strand monad must be evaluted in a particular way to maintain
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:: its monadic character. +take:eval implements this.
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::
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++ eval
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|%
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:: Indelible state of a strand
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::
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+$ eval-form
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$: =form
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==
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::
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:: Convert initial form to eval-form
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::
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++ from-form
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|= =form
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^- eval-form
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form
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::
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:: The cases of results of +take
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::
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+$ eval-result
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$% [%next ~]
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[%fail err=(pair term tang)]
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[%done value=a]
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==
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::
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:: Take a new sign and run the strand against it
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::
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++ take
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:: cards: accumulate throughout recursion the cards to be
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:: produced now
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=| cards=(list card)
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|= [=eval-form =strand-input]
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^- [[(list card) =eval-result] _eval-form]
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=* take-loop $
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:: run the strand callback
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::
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=/ =output (form.eval-form strand-input)
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:: add cards to cards
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::
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=. cards
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%+ welp
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cards
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:: XX add tag to wires?
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cards.output
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:: case-wise handle next steps
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::
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?- -.next.output
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%wait [[cards %next ~] eval-form]
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%skip [[cards %next ~] eval-form]
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%fail [[cards %fail err.next.output] eval-form]
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%done [[cards %done value.next.output] eval-form]
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%cont
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:: recurse to run continuation with initialization input
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::
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%_ take-loop
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form.eval-form self.next.output
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strand-input [bowl.strand-input ~]
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==
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==
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--
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--
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--
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