From: William Hubbs <williamh@gentoo.org>
To: gentoo-dev@lists.gentoo.org
Subject: Re: [gentoo-dev] Re: RFC: USE flags in virtuals, to allow a specific provider to be determined
Date: Sun, 27 Jul 2014 10:38:49 -0500 [thread overview]
Message-ID: <20140727153849.GA17979@linux1> (raw)
In-Reply-To: <53D3E94A.9000100@gentoo.org>
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On Sat, Jul 26, 2014 at 01:45:46PM -0400, Jonathan Callen wrote:
*snip*
> If you want to say "At most one of the flags 'foo', 'bar', and 'baz'
> may be selected", then you say it like so (requires EAPI=5):
>
> REQUIRED_USE="?? ( foo bar baz )"
>
> If you want to say "Exactly one of the flags ...", then you use:
>
> REQUIRED_USE="^^ ( foo bar baz )"
>
> And, as always, you can say "At least one of the flags ..." with:
>
> REQUIRED_USE="|| ( foo bar baz )"
>
> While each of these can be written using the "foo? ( !bar )"-type
> primitives, the messages portage outputs are generally better with
> '??', '^^', and '||', as you might see something like:
>
> "
> The following REQUIRED_USE flag constraints are unsatisfied:
> at-most-one-of ( foo bar baz )
> "
>
> Which is, in my opinion, more readable.
Now I understand what ciaranm was suggesting in pkg_pretend. Note, this
is not shell syntax, but it conveys the idea...
pkg_pretend() {
count=0
for x in foo bar bas; do
use $x && count += 1
done
# Now, if count == 0 none of the flags are used, and
# if count > 1 more than one is used, so die whenever appropriate
# with any error message you choose.
}
William
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next prev parent reply other threads:[~2014-07-27 15:39 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-25 18:49 [gentoo-dev] RFC: USE flags in virtuals, to allow a specific provider to be determined Ian Stakenvicius
2014-07-25 19:04 ` Luis Ressel
2014-07-25 19:23 ` Ian Stakenvicius
2014-07-25 19:44 ` Luis Ressel
2014-07-25 19:46 ` Ciaran McCreesh
2014-07-25 19:49 ` Ian Stakenvicius
2014-07-25 19:51 ` Pacho Ramos
2014-07-25 19:54 ` Ian Stakenvicius
2014-07-25 20:12 ` Pacho Ramos
2014-07-25 20:18 ` Ciaran McCreesh
2014-07-26 8:28 ` Pacho Ramos
2014-07-25 21:13 ` Ian Stakenvicius
2014-07-25 21:25 ` Ciaran McCreesh
2014-07-25 21:23 ` William Hubbs
2014-07-25 21:25 ` Ciaran McCreesh
2014-07-25 21:46 ` William Hubbs
2014-07-25 21:50 ` Ciaran McCreesh
2014-07-26 17:45 ` [gentoo-dev] " Jonathan Callen
2014-07-27 15:38 ` William Hubbs [this message]
2014-07-25 20:41 ` [gentoo-dev] " Michał Górny
2014-07-25 21:09 ` Ian Stakenvicius
2014-07-26 7:17 ` justin
2014-07-26 8:05 ` [gentoo-dev] " Duncan
2014-07-26 8:30 ` Pacho Ramos
2014-07-26 8:53 ` Michał Górny
2014-07-26 9:01 ` Duncan
2014-07-26 12:46 ` Ciaran McCreesh
2014-07-26 8:58 ` Duncan
2014-07-26 13:31 ` Ian Stakenvicius
2014-07-26 14:40 ` [gentoo-dev] " Manuel Rüger
2014-07-27 17:11 ` Peter Stuge
2014-07-28 14:20 ` Ian Stakenvicius
2014-07-28 14:42 ` Michał Górny
2014-07-28 15:11 ` Ian Stakenvicius
2014-07-28 11:21 ` Michał Górny
2014-07-28 17:02 ` Ian Stakenvicius
2014-07-29 4:23 ` James Potts
2014-07-29 11:06 ` Ciaran McCreesh
2014-07-29 4:51 ` Michał Górny
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