Appendix A Emacs 24 Antinews

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 25.1 features.

A.1 Old Lisp Features in Emacs 24

• The requirement that setq and 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 nil for the missing one. Simplicity rules!
• M-x shell and M-x compile set the 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.
• The save-excursion form saves and restores the mark, as expected. No more need for the new save-mark-and-excursion, which has been deleted.
• We have removed the 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, 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.
• Regular expressions have been simplified by removing support for Unicode character properties in regexp classes. As result, [:alpha:] and [:alnum:] will match any character with a word syntax, and [:graph:] and [: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.
• Evaluating ‘(/ n)’ will now yield n. We have realized that interpreting that as in Common Lisp was a bad mistake that needed to be corrected.
• The pcase form was significantly simplified by removing the UPatterns quote and app. To further simplify this facility, we’ve removed pcase-defmacro, since we found no need for letting Lisp programs define new UPatterns.
• We’ve removed the text properties cursor-intangible and cursor-sensor-functions, replacing them by the much simpler intangible, point-entered, and point-left properties. The latter are implemented on a much lower level, and therefore are better integrated with user expectations. For similar reasons, cursor-intangible-mode and cursor-sensor-mode were removed; use the hook variable inhibit-point-motion-hooks which is no longer obsolete.
• Process creation and management functions were significantly improved and simplified by removing make-process and the pipe connection type. Redirecting stderr of a subprocess should be done with shell facilities, not by Emacs.
• We decided that shutting up informative messages is bad for user interaction, so we’ve removed the inhibit-message variable which could be used to that effect.
• Support for generators and for finalizers has been removed, as we found no real need for these facilities.
• Due to excessive complexity and the diminishing need for Unicode support, the functions string-collate-lessp and string-collate-equalp were removed. Their locale-independent counterparts string-lessp and 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 ls-lisp.el package sorts files in a locale-independent manner.
• In preparation for removal in some past version of Emacs of the bidirectional editing support, we started by deleting two functions bidi-find-overridden-directionality and buffer-substring-with-bidi-context.
• Time conversion functions, such as current-time-string, no longer accept an optional zone argument. If you need to change the current time zone (why?), do that explicitly with set-time-zone-rule.
• As part of the ongoing quest for simplicity, many other functions and variables have been eliminated.