Re: lua-l Digest, Vol 58, Issue 58

[Александр Машин <alex.mashin@...>]

> Dear all,
>
> I am trying to write a parser that would process some wikitext--text
>  with wikilinks [[page|(optional alias)]] (but not escaped [[:page]])
> inside.
>
> I want it to return the passed string itself (with some alterations),
> a list of referred pages and the symbol that is likely to be the list
>  separator in the string passed.
>
> I wrote the following grammar:
>
> wikitext             <- {| { {| ( prefix?  wikilink )+ |} tail } |}
> wikilink              <- unescapedopen page alias? close
> page <- { ( !close !pipe . )+ }
>alias                   <- pipe ( !close . )*
> tail                     <- .*
>prefix                 <- ( separator / ( !unescapedopen . ) )+
> open                  <- "[["
> unescapedopen <- open !escape
>close                  <- "]]"
>pipe <- "|"
>escape              <- ":"
>separator          <- {:separator: [,;*#] :} space*
> space                <- %s
>
>
> After applying it (re.match) to the example line "Perhaps,
> [[Peter|Simon]], or [[Paul]], so they say", I got:
>
> table {
>1 = Perhaps, [[Peter|Simon]], or [[Paul]], so they say
> 2 = table {
> 1 = Peter
> 2 = Paul
> separator = ,
> }
> }
>
> This is close to what I want.
>
> However, there are some issues: 1) can I make outer table's indices
> strings: ['full'] not [1], ['items'] not [2]? I experimented with
> named group captures but unsuccessfully. 2) can the number of nested
> captures be reduced? 3) most importantly: I want a string constant
> (e.g. "Name::") to be inserted after any found <unescapedopen>; and
> the first capture that returns the whole line should contain this
> constant: "...[[Name::Paul]]..." not "...[[Paul]]...". This can have
> something to do with substitution captures; I tried them but couldn't
> do it. Can it be done at all?

> Unsuccessfully meaning what?I've used named group captures
> successfully.
So have I but not in this case. I coudn't make numbered table items 
named by replacing simple captures with named group ones.


>> 2) can the number of nested captures be reduced?
> Not sure what you mean.
There are four levels of captures to make two levels of tables. Perhaps, 
this could have been achieved with fewer.

> > 3) most importantly: I want  a string constant (e.g. "Name::") to be
>> inserted after any found <unescapedopen>;
> Try: ''->'Name::'  (Match an empty string and capture Name::)
No, I tried this (both within {~ ~} and not), and it didn't work.

Alexander Mashin