censig, `%~`, %cnsg

Pull with sample

%~ is a synthetic rune that pulls p from the door q with its sample set to r. %~ is used to produce an arm p inside of a door q with the door's sample set to r.

Produces

Twig: [%cnsg p=wing q=twig r=twig]

Sample

p is a wing. q and r are twigs.

Tall form

%~  p
  q
r

Wide form

%~(p q r)

Irregular form

~(p q r)

Examples

/~zod/try=> =door  |_  a=@
                   ++  fort  |=  b=@
                             (add b a)
                   --
new var %door
/~zod/try=> (~(fort door 10) 1)
11
/~zod/try=> (~(fort door 10) 10)
20

Here we create a door using |_ as the shell variable door which takes an atom. door has one arm fort, a gate, which takes an atom as well and produces the sum. We use the irregular form of %~ to set the sample in door, and call it.

/~zod/try=> =a  (mo (limo [['a' 1] ['b' 2] ~]))
changed %a
/~zod/try=> a
{[p='a' q=1] [p='b' q=2]}
/~zod/try=> (~(get by a) 'b')
[~ 2]

In this case we create a simple map, a using ++mo and '++limo'. Then we use ++get:by to pull a value out of it by first setting the sample of ++by to a and pulling get using the irregular form of %~. Passing 'b' to the resulting gate produces the value of 'b' in our map.

This is a very common use of %~. Most of the container engines in hoon.hoon use doors with samples, so we use %~ to set the sample and pull the door to produce a gate we can pass data to.

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censig, %~, %cnsg