The input to a strand
is defined in /lib/strand/hoon
as:
+$ strand-input [=bowl in=(unit input)]
When a thread is first started, spider will populate the bowl
and provide it along with an input
of ~
. If/when new input comes in (such as a poke, sign or watch) it will provide a new updated bowl along with the new input.
For example, here's a thread that gets the time from the bowl, runs an IO-less function that takes one or two seconds to compute, and then gets the time again:
/- spider
/+ *strandio
=, strand=strand:spider
|%
++ ackermann
|= [m=@ n=@]
?: =(m 0) +(n)
?: =(n 0) $(m (dec m), n 1)
$(m (dec m), n $(n (dec n)))
--
^- thread:spider
|= arg=vase
=/ m (strand ,vase)
^- form:m
;< t1=@da bind:m get-time
=/ ack (ackermann 3 8)
;< t2=@da bind:m get-time
(pure:m !>([t1 t2]))
Since it never does any IO, t1
and t2
are the same: [~2021.3.17..07.47.39..e186 ~2021.3.17..07.47.39..e186]
. However, if we replace the ackermann function with a 2 second sleep
from strandio:
/- spider
/+ *strandio
=, strand=strand:spider
^- thread:spider
|= arg=vase
=/ m (strand ,vase)
^- form:m
;< t1=@da bind:m get-time
;< ~ bind:m (sleep ~s2)
;< t2=@da bind:m get-time
(pure:m !>([t1 t2]))
...and run it again we get different values for t1
and t2
: [~2021.3.17..07.50.28..8a5d ~2021.3.17..07.50.30..8a66]
. This is because sleep
gets a %wake
sign back from behn
, so spider updates the time in the bowl along with it.
Now let's look at the contents of bowl
and input
in detail:
bowl
bowl
is the following:
+$ bowl
$: our=ship
src=ship
tid=tid
mom=(unit tid)
wex=boat:gall
sup=bitt:gall
eny=@uvJ
now=@da
byk=beak
==
our
- our shipsrc
- ship where input is coming fromtid
- ID of this threadmom
- parent thread if this is a child threadwex
- outgoing subscriptionssup
- incoming subscriptionseny
- entropynow
- current datetimebyk
-[p=ship q=desk r=case]
path prefix
There are a number of functions in strandio
to access the bowl
contents like get-bowl
, get-beak
, get-time
, get-our
and get-entropy
.
You can also write a function with a gate whose sample is strand-input:strand
and access the bowl that way like:
/- spider
/+ strandio
=, strand=strand:spider
=>
|%
++ bowl-stuff
=/ m (strand ,[boat:gall bitt:gall])
^- form:m
|= tin=strand-input:strand
`[%done [wex.bowl.tin sup.bowl.tin]]
--
^- thread:spider
|= arg=vase
=/ m (strand ,vase)
^- form:m
;< res=[boat:gall bitt:gall] bind:m bowl-stuff
(pure:m !>(res))
input
input
is defined in libstrand as:
+$ input
$% [%poke =cage]
[%sign =wire =sign-arvo]
[%agent =wire =sign:agent:gall]
[%watch =path]
==
%poke
incoming poke%sign
incoming sign from arvo%agent
incoming sign from a gall agent%watch
incoming subscription
Various functions in strandio
will check input
and conditionally do things based on its contents. For example, sleep
sets a behn
timer and then calls take-wake
to wait for a %wake
sign from behn:
++ take-wake
|= until=(unit @da)
=/ m (strand ,~)
^- form:m
|= tin=strand-input:strand
?+ in.tin `[%skip ~]
~ `[%wait ~]
[~ %sign [%wait @ ~] %behn %wake *]
?. |(?=(~ until) =(`u.until (slaw %da i.t.wire.u.in.tin)))
`[%skip ~]
?~ error.sign-arvo.u.in.tin
`[%done ~]
`[%fail %timer-error u.error.sign-arvo.u.in.tin]
==