Re: A Lua pattern question about optional patterns

[Thorkil Naur <naur@...>]

Hello Phil,

On Wed, Sep 11, 2019 at 05:49:01PM +0000, Phil Leblanc wrote:
> I looked for the %z pattern in the manual (Lua 5.3, 5.4-alpha-rc2) but
> didn't find it.

In

  https://www.lua.org/manual/5.2/manual.html
  8.2 – Changes in the Libraries

you'll find

  Character class %z in patterns is deprecated, as now patterns may
  contain '\0' as a regular character.

Nevertheless, %z is still supported by at least the Lua 5.3.4 I checked:

> $ awk '/static int match_class/,/^}/' lstrlib.c
> static int match_class (int c, int cl) {
>   int res;
>   switch (tolower(cl)) {
>     case 'a' : res = isalpha(c); break;
>     case 'c' : res = iscntrl(c); break;
>     case 'd' : res = isdigit(c); break;
>     case 'g' : res = isgraph(c); break;
>     case 'l' : res = islower(c); break;
>     case 'p' : res = ispunct(c); break;
>     case 's' : res = isspace(c); break;
>     case 'u' : res = isupper(c); break;
>     case 'w' : res = isalnum(c); break;
>     case 'x' : res = isxdigit(c); break;
>     case 'z' : res = (c == 0); break;  /* deprecated option */
>     default: return (cl == c);
>   }
>   return (islower(cl) ? res : !res);
> }
>
> $

Best regards
Thorkil