Re: [gentoo-dev] Pre-GLEP RFC: Automated enforcing of REQUIRED_USE constraints

[Alexis Ballier]

On Sat, 8 Jul 2017 21:05:57 +0200
Ulrich Mueller <ulm@g.o> wrote:

> >>>>> On Sat, 8 Jul 2017, Ciaran McCreesh wrote:
>
> > On Sat, 8 Jul 2017 16:39:29 +0200
> > Alexis Ballier <aballier@g.o> wrote:
> >> Indeed, makes sense. Would it also make sense to have some more
> >> logical meaning in a future EAPI ? I mean, in every context I've
> >> ever seen, applying a rule to the empty set is the neutral of that
> >> rule, so that it preserves associativity.
> >> That'd mean: || ( ) is false, && ( ) is true, ^^ ( ) is false,
>
> I have no strong opinion about this. Is it worth the effort of
> changing the spec?
>
> >> ?? ( ) is false.
>
> I think ?? ( ) aka at-most-one-of should be true if empty.

Maybe; this one is annoying I think since it is not associative per
definition:
?? ( true ?? ( false false ) ) -> ?? ( true true ) -> false
?? ( ?? ( true false ) false ) -> ?? ( true false) -> true


> > The sensible thing to do is ban it, and additionally ban use? ( )
> > inside || and ^^ (if we've not done that already...).
>
> Right. We have to check if this will break any eclass generated
> dependencies, though.

That's probably the best course of action indeed.

Alexis.