Re: [gentoo-dev] Re: use flags -> use options

[Marijn Schouten (hkBst)]

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Marius Mauch wrote:
>>> "Marijn Schouten (hkBst)" <hkBst@g.o>:
>>>> I imagine there are a lot more cases where the simple on/off
>>>> system we have now is suboptimal. I could be wrong of course.
>>>> Please comment.
>>>  This key=value systems sounds interesting.  Another use could be
>>> the choice between xulrunner, seamonkey, firefox.
>
> We already have this with USE_EXPAND. Not exactly the same syntax, but
> I don't see a terrible problem in that, and we don't have to fix all
> three trillion related tools to handle it. Unless you can come up
> with a case that can't be handled with USE_EXPAND.

No, USE_EXPAND is only a way to abbreviate use flags with a common substring
in their name, such as "impl_guile impl_sbcl impl_clisp" which could be
encoded interchangeably as either

# without USE_EXPAND
IUSE="impl_guile impl_sbcl impl_clisp"

or

# with USE_EXPAND
for impl in IMPL; do IUSE+="impl_${impl}"; done

but the effect is that there are 3 use flags with a total of 2^3=8
combinations, while really something with exactly 3 combinations is needed:

IUSE="impl"

case ${impl} in
	guile)  #use guile as backend
	 sbcl)  #use sbcl  as backend
	clisp)  #use clisp as backend

or something like that.

Marijn

- --
Marijn Schouten (hkBst), Gentoo Lisp project
<http://www.gentoo.org/proj/en/lisp/>, #gentoo-lisp on FreeNode
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