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Re: compat unification

From: Lars Magne Ingebrigtsen
Subject: Re: compat unification
Date: Tue, 16 Nov 2010 16:44:07 +0100
User-agent: Gnus/5.110011 (No Gnus v0.11) Emacs/24.0.50 (gnu/linux)

Stefan Monnier <address@hidden> writes:

> It couldn't be part of Emacs: Emacs-22's ems-compat wouldn't be able to
> come with Emacs-24's compatibility functions, would it?
> So it'd have to be an ELPA package.

The ems-compat library would support *all* previous Emacs and XEmacs
instances -- so there would only be one, was my thought.

But having it in ELPA would work, too.

> You can go some way with such a package, but it has significant limits.
> E.g. you'll still often want to know whether a feature is supported or
> not before using it, because you'll want to use some other code if
> it's not.

Yes, and it doesn't really help with functions that do exist, but take
different parameters, for instance.  (Those are thankfully somewhat
rare.)  And variables that you bind to achieve an effect are difficult
to do anything with...

So it's not exactly a panacea...  

> Also such compatibility definitions may confuse other packages who'd
> check (fboundp 'foo) to see if a particular feature is present.

Yes, that's been the main objection to doing this in the past.
However -- packages really should check for features, and not the
presence of functions, so we could declare doing that as an error.  I'm
not sure what the impact would be, though.

(domestic pets only, the antidote for overdose, milk.)
  address@hidden * Lars Magne Ingebrigtsen

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