urbit/pub/doc/hoon/runes/dt/dtwt.md
2015-06-19 17:16:48 -04:00

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[dotwut,`.?`, %dtwt](#dtwt)
===========================
Noun or cell
`.?`, `dotwut`, `[%dtwt p=twig]` is a natural hoon that applies nock `3`
to a noun: if the noun is a cell, it returns the loobean `&` (true); if
the noun is an atom, it returns the loobean `|` (false).
Produces
--------
Twig: `[%dtwt p=twig]`
Sample
------
`p` is a [twig]().
Tall form
---------
.? p
Wide form
---------
.?(p)
Irregular form
--------------
None
Examples
--------
~zod/try=> .?(~)
%.n
~zod/try=> .?(5)
%.n
~zod/try=> .?(~porlep)
%.n
In all of these cases our sample is implicitly down-cast to an atom,
which produces `|`.
~zod/try=> .?([1 2 3])
%.y
~zod/try=> .?("ha")
%.y
~zod/try=> ._a_b__
[%a %b]
~zod/try=> .?(._a_b__)
%.y
`[1 2 3]` is clearly a cell, `"ha"` is equivalent to the null-terminated
tuple of its ASCII codes, and `._a_b__` is also clearly a cell. Each
produce `&`.