Re: Shortcut for \repeat unfold

[Hans Åberg]

> On 26 Sep 2021, at 06:49, Werner LEMBERG <wl@gnu.org> wrote:
> 
>>>> The idea here is different, it is for identifiers, and in the
>>>> input syntax only, does not change the internal semantics at all.
>>>> It is good not having to type backslash when a command is used.
>>> 
>>> Really?  I highly doubt that.  In particular, what about lyrics
>>> mode?
>> 
>> The idea would be to change the file lexer.ll by adding U and
>> UCOMMAND:
>> 
>> A            [a-zA-Z\200-\377]
>> U            [\200-\377]
>> AA           {A}|_
>> N            [0-9]
>> ANY_CHAR     (.|\n)
>> SYMBOL       {A}([-_]{A}|{A})*
>> COMMAND      \\{SYMBOL}
>> UCOMMAND     {U}{SYMBOL}
>> 
>> Then in select places, that is context switches, add {UCOMMAND}:
>>      {COMMAND}       {
>>              return scan_escaped_word (YYText_utf8 () + 1);
>>      }
>>      {UCOMMAND}      {
>>              return scan_escaped_word (YYText_utf8 ());
>>      }
> 
> You might provide a MR, maybe it gets accepted.  I still doubt that it
> would be a good idea.

There is a conflict in some contexts between {SYMBOL} and {COMMAND}, so may not 
work. To get a regular COMMAND syntax, they should start with something that 
SYMBOL does not.

Otherwise you might replace the function YYText_utf8 with proper UTF-8 
patterns, a variation of:

/* UTF-8 character with valid Unicode code point. */
utf8char    
[\x09\x0A\x0D\x20-\x7E]|[\xC2-\xDF][\x80-\xBF]|\xE0[\xA0-\xBF][\x80-\xBF]|[\xE1-\xEC\xEE\xEF]([\x80-\xBF]{2})|\xED[\x80-\x9F][\x80-\xBF]|\xF0[\x\90-\xBF]([\x80-\xBF]{2})|[\xF1-\xF3]([\x80-\xBF]{3})|\xF4[\x80-\x8F]([\x80-\xBF]{2})