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RE: How to find when a feature was introduced
From: |
Drew Adams |
Subject: |
RE: How to find when a feature was introduced |
Date: |
Fri, 8 Jul 2016 05:44:47 +0000 (UTC) |
> > > So now I need to tell my students gnu-apl-mode will not run in emacsen
> > > less than version X How to find out X?
>
> M-x view-emacs-news RET C-s FEATURE
That works for some features/functions/variables/..., but not for
others. It depends on how well and even whether the thing in question
is called out clearly in the NEWS.
FWIW -
I keep multiple Emacs binaries and check them when needed. But I do
that because I maintain some of my libraries across multiple releases.
(Many people will not bother to do this.)
If I have a library that fundamentally makes use of some feature that
is only available starting with release N.M then that's the minimum
release I support for that library - e.g., `apu.el' is Emacs 24+
because it is all about Unicode.
But if a library just makes incidental use of some feature - it is
not essential to the library, then I support older releases that
don't provide that feature, and I conditionalize its use within
the library using `fboundp', `boundp', `featurep', or even a
release-number check, whichever is most specific but still
sufficient to distinguish whatever is involved.
Yes, that means extra maintenance work. But there are lots of
Emacs users (most!) who do _not_ use the latest release. I see
too many libraries (IMHO) that evolve to gratuitously use recent
constructs, which means some of their users can lose the
possibility of using them.
By "gratuitously" here I mean that the library maintainer and the
library itself do not really gain anything important by such a
change. Obviously, if a new feature enables you to do something
really different (e.g. bidi support) or really better, then there
is no reason not to take advantage of it.
But many changes I see are little more than cosmetic, and if such
a case throws library users by the wayside then I think that's a
waste. On the other hand, it can make things easier for a library
maintainer not to have to worry about supporting more than the
latest release...
YMMV
Re: How to find when a feature was introduced, Eli Zaretskii, 2016/07/08