Re: {{ double braces }}

[Taco Hoekwater <taco@elvenkind.com>]

Thomas A. Schmitz wrote:
> 
> You could also use a nice scripting language like ... lua!! lua has  
> support for "balanced strings," so no nesting trickery is needed, 
> see http://www.lua.org/pil/20.2.html 
>   (scroll to the bottom of the page). Or you could try and nag Hans  
> into giving a nice tutorial on the lua lpeg library at Bohinj! :-)

Even in bare lua, it is very easy to match balanced braces:

   local data = "\\footnote{x{y}z}"

   local match = "\\footnote%s%b{}"
   local i = 0
   while true do
      i,j = string.find(data, match, i+1)
      if i == nil then break end
      print(string.sub(data, i, j))
   end

with lpeg, the code looks a bit harder, but is still short and
relatively shortforward:

   local matchtable = { "TEXT",
     SP = lpeg.S" \n\t"^0,
     BODY = lpeg.P{ "{" * ((1 - lpeg.S"{}") + lpeg.V(1))^0 * "}" },
     FOOTNOTE = lpeg.P"\\footnote" * lpeg.V"SP" * lpeg.V"BODY" / print,
     TEXT = (lpeg.V"FOOTNOTE" + 1)^0 * -1,
   }
   lpeg.match(matchtable, data)

Best wishes,
Taco
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