urbit/base/pub/doc/hoon/runes/zp/zpwt.md
2015-04-29 18:48:45 -04:00

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[zapwut, `!?`, %zpwt](#zpwt)
============================
Restrict version
`!?` is a synthetic rune that enforces a Hoon version restriction.
Produces
--------
Twig: `[%zpwt p=twig]`
Sample
------
`p` is a [twig]().
Tall form
---------
To declare code that runs only in Hoon 164K or newer:
!? 164
q
To declare code that runs only in 164K through 161K:
!? [164 161]
q
Wide form
---------
None
Irregular form
--------------
None
Examples
--------
~zod/try=> !?(264 (add 2 2))
4
~zod/try=> !?(164 (add 2 2))
4
~zod/try=> !?(163 (add 2 2))
! exit