Re: Upcoming loss of usability of Emacs source files and Emacs.

[Ulrich Mueller]

>>>>> On Wed, 17 Jun 2015, Marcin Borkowski wrote:

> On the other hand, it would be great if we had an "ascii-folding"
> option, making (some reasonable subset of) Unicode "equivalent" to
> ASCII, so that we could easily search for e.g. the Polish word ‘żółw’
> (meaning "turtle") by typing `zolw'.  (I have to say that lack of this
> is one of my main gripes with A****n's K****e e-book reader - this
> renders the "search" option unusable for non-English texts...)

I have the following code in my .emacs which does exactly that:

;; Ignore accent and umlaut marks when searching.
;; Works for Emacs 19.30 and later.
(let ((eqv-list '("aAàÀáÁâÂãÃäÄåÅ"
                  "cCçÇ"
                  "eEèÈéÉêÊëË"
                  "iIìÌíÍîÎïÏ"
                  "nNñÑ"
                  "oOòÒóÓôÔõÕöÖøØ"
                  "uUùÙúÚûÛüÜ"
                  "yYýÝÿ"))
      (table (standard-case-table))
      canon)
  (setq canon (copy-sequence table))
  (mapcar (lambda (s)
            (mapcar (lambda (c) (aset canon c (aref s 0))) s))
          eqv-list)
  (set-char-table-extra-slot table 1 canon)
  (set-char-table-extra-slot table 2 nil)
  (set-standard-case-table table))

Maybe it could be used as the basis for a minor mode? Downside is that
the above will significantly slow down search in multibyte buffers.
This is because equivalent characters have a different number of bytes
in UTF-8, therefore the Boyer-Moore algorithm cannot be used any more.

Ulrich