mirror of
https://github.com/ilyakooo0/urbit.git
synced 2024-12-20 21:31:32 +03:00
79 lines
1.6 KiB
Markdown
79 lines
1.6 KiB
Markdown
|
[barhep, `|-`, %brhp](#brhp)
|
||
|
|
============================
|
||
|
|
|
||
|
|
Kicked trap
|
||
|
|
|
||
|
|
`|-` is a synthetic rune that produces a dry [`%gold`]() trap and
|
||
|
|
[kicks]() it. You can think of a trap like a 'trap door', since `|-` is
|
||
|
|
a [`door`]() with only one arm [`$`](), the empty name.
|
||
|
|
|
||
|
|
`|-` is different from `|.` in that it is kicked by default. `|-` is
|
||
|
|
similar to creating and calling an anonymous function and is quite
|
||
|
|
commonly used for loops or recursion.
|
||
|
|
|
||
|
|
See also
|
||
|
|
--------
|
||
|
|
|
||
|
|
[bardot, `|.`, %brdt](#brdt)
|
||
|
|
|
||
|
|
Produces
|
||
|
|
--------
|
||
|
|
|
||
|
|
Twig: `[%brhp p=twig]`
|
||
|
|
|
||
|
|
Sample
|
||
|
|
------
|
||
|
|
|
||
|
|
`p` is a twig
|
||
|
|
|
||
|
|
Tall form
|
||
|
|
---------
|
||
|
|
|
||
|
|
|- p
|
||
|
|
|
||
|
|
Wide form
|
||
|
|
---------
|
||
|
|
|
||
|
|
|-(p)
|
||
|
|
|
||
|
|
Irregular form
|
||
|
|
--------------
|
||
|
|
|
||
|
|
None
|
||
|
|
|
||
|
|
Examples
|
||
|
|
--------
|
||
|
|
|
||
|
|
/~zod/try=> |-(42)
|
||
|
|
42
|
||
|
|
|
||
|
|
In contrast to our `|.` example, `|-` is kicked by default, so its
|
||
|
|
internals are produced immediately.
|
||
|
|
|
||
|
|
/~zod/try=> =+ a=`*`~[41 42]
|
||
|
|
|-
|
||
|
|
?~ a
|
||
|
|
~
|
||
|
|
[-.a %m $(a +.a)]
|
||
|
|
[41 %m [42 %m ~]]
|
||
|
|
|
||
|
|
In this case we use `|-` for one of its most common applications, a
|
||
|
|
loop. Here we walk across `a` by calling `$` with `a` replaced by `+.a`,
|
||
|
|
producing a nested tuple.
|
||
|
|
|
||
|
|
++ dec :: decrement
|
||
|
|
~/ %dec
|
||
|
|
|= a=@
|
||
|
|
~| %decrement-underflow
|
||
|
|
?< =(0 a)
|
||
|
|
=+ b=0
|
||
|
|
|- ^- @
|
||
|
|
?: =(a +(b))
|
||
|
|
b
|
||
|
|
$(b +(b))
|
||
|
|
|
||
|
|
In `++dec`, found in `hoon.hoon`, `|-` creates a trap that contains the
|
||
|
|
test and looping semantics. Essentially, we count up to `a-1` by
|
||
|
|
incrementing `b`. Using `|-` inside an existing core as we do here is
|
||
|
|
its most common use.
|