bug#21816: elisp-mode-tests fails on a case-preserving filesystem

[Alexis <flexibeast@gmail.com>]

Random832 <random832@fastmail.com> writes:

> Alexis <flexibeast@gmail.com> writes: 
>> Perhaps use German Eszett / sharp S / Unicode LATIN SMALL 
>> LETTER SHARP S? The words 'Strasse' and 'Straße' are 
>> equivalent, but typically the latter is up-cased to 'STRASSE', 
>> rather than 'STRAẞE'.
>
> Fsvo "typically".

Oh, sorry, by "typically", i meant "when writing in German", not 
"when doing case-conversions in computing".

> On Emacs, and in Windows filenames [fortuitously, they match in 
> this case. Unfortunately, I don't believe there's an easy way to 
> get at the table used in Windows], upcasing is done on a 
> character-by-character basis, and AIUI neither of them do this, 
> so (string= (upcase "Straße") "STRAßE").

*nod* A good example of why i think the Eszett might be useful for 
testing any proposed equivalence-relation or canonicalisation code 
- there are a variety of approaches "in the wild" re. TRT. Take 
SRFI 75, for example:

https://www.cs.utah.edu/~mflatt/tmp/srfi-75.html

in the section "String Procedures":

    (string<? "z" "ß") => #t (string<? "z" "zz") => #t (string<? 
    "z" "Z") => #f (string=? "Straße" "Strasse") => #f 
 
    (string-upcase "Hi") => "HI" (string-downcase "Hi") => "hi" 
    (string-foldcase "Hi") => "hi" 
 
    (string-upcase "Straße") => "STRASSE" (string-downcase 
    "Straße") => "straße" (string-foldcase "Straße") => "strasse" 
    (string-downcase "STRASSE")  => "strasse"


Alexis.