@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1999, 2002-2017 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.

@c This node must have no pointers.

@node Antinews
@appendix Emacs 24 Antinews
@c Update the elisp.texi Antinews menu entry with the above version number.

For those users who live backwards in time, here is information about
downgrading to Emacs version 24.5.  We hope you will enjoy the greater
simplicity that results from the absence of many Emacs @value{EMACSVER}
features.

@section Old Lisp Features in Emacs 24

@itemize @bullet
@item
The requirement that @code{setq} and @code{setf} must be called with
an even number of arguments has been removed.  You can now call them
with an odd number of arguments, and Emacs will helpfully supply a
@code{nil} for the missing one.  Simplicity rules!

@item
@kbd{M-x shell} and @kbd{M-x compile} set the @env{EMACS} environment
variable, as they should, to indicate that the subprocess is run by
Emacs.  This is so packages that took years to learn how to work
around that setting could continue using their code to that effect.

@item
The @code{save-excursion} form saves and restores the mark, as
expected.  No more need for the new @code{save-mark-and-excursion},
which has been deleted.

@item
We have removed the @code{text-quoting-style} variable and the
associated functionality that translates quote characters in messages
displayed to the user and in help buffers.  Emacs now shows exactly
the same quote characters as you wrote in your code!  Likewise,
@code{substitute-command-keys} leaves the quote characters alone.  As
you move back in time, Unicode support becomes less and less
important, so no need to display those fancy new quotes the Unicode
Standard invented.

@item
Regular expressions have been simplified by removing support for
Unicode character properties in regexp classes.  As result,
@code{[:alpha:]} and @code{[:alnum:]} will match any character with a
word syntax, and @code{[:graph:]} and @code{[:print:]} will match any
multibyte character, including surrogates and unassigned codepoints.
Once again, this is in line with diminishing importance of Unicode as
you move back in time.

@item
Evaluating @samp{(/ @var{n})} will now yield @var{n}.  We have
realized that interpreting that as in Common Lisp was a bad mistake
that needed to be corrected.

@item
The @code{pcase} form was significantly simplified by removing the
UPatterns @code{quote} and @code{app}.  To further simplify this
facility, we've removed @code{pcase-defmacro}, since we found no need
for letting Lisp programs define new UPatterns.

@item
We've removed the text properties @code{cursor-intangible} and
@code{cursor-sensor-functions}, replacing them by the much simpler
@code{intangible}, @code{point-entered}, and @code{point-left}
properties.  The latter are implemented on a much lower level, and
therefore are better integrated with user expectations.  For similar
reasons, @code{cursor-intangible-mode} and @code{cursor-sensor-mode}
were removed; use the hook variable @code{inhibit-point-motion-hooks}
which is no longer obsolete.

@item
Process creation and management functions were significantly improved
and simplified by removing @code{make-process} and the @code{pipe}
connection type.  Redirecting @code{stderr} of a subprocess should be
done with shell facilities, not by Emacs.

@item
We decided that shutting up informative messages is bad for user
interaction, so we've removed the @code{inhibit-message} variable
which could be used to that effect.

@item
Support for generators and for finalizers has been removed, as we
found no real need for these facilities.

@item
Due to excessive complexity and the diminishing need for Unicode
support, the functions @code{string-collate-lessp} and
@code{string-collate-equalp} were removed.  Their locale-independent
counterparts @code{string-lessp} and @code{string-equal} are so much
more simple and yield predictable results that we don't see any
situation where the locale-dependent collation could be useful in
Emacs.  As result, the @file{ls-lisp.el} package sorts files in a
locale-independent manner.

@item
In preparation for removal in some past version of Emacs of the
bidirectional editing support, we started by deleting two functions
@code{bidi-find-overridden-directionality} and
@code{buffer-substring-with-bidi-context}.

@item
Time conversion functions, such as @code{current-time-string}, no
longer accept an optional @var{zone} argument.  If you need to change
the current time zone (why?), do that explicitly with
@code{set-time-zone-rule}.

@item
As part of the ongoing quest for simplicity, many other functions and
variables have been eliminated.
@end itemize