Re: [LPeg] How can I make a recursive pattern?

["Soni L." <fakedme@...>]

On 27/07/16 12:34 PM, Patrick Donnelly wrote:
> Soni,
>
> On Wed, Jul 27, 2016 at 10:27 AM, Soni L. <fakedme@gmail.com> wrote:
> > Sean Conner's incomplete solution uses lpeg.Carg(1) which doesn't work
> > recursively.
> >
> > This is what I'm trying to parse: https://github.com/SoniEx2/MDXML
> >
> > This is what I currently have:
> > [...]
> Most people don't have time to grok your code. Can you give a smaller
> example/explanation of what you're trying to do? It sounds like you
> may want to use group and back captures to carry information in
> recursive matching. Not sure though...
Basically (really oversimplifying here) I have:

tag = # <stuff> \n
tagns = #### <stuff> \n
attr = ## <stuff> \n
val = ### <stuff> \n
atrrns = ##### <stuff> \n
content = > <stuff> [\n > <stuff>] \n \n

and I want to capture things like:

tag and {
  [0] = tagns and {tag=tag.stuff, ns=tagns.stuff} or tag.stuff,
  [attr.stuff] = attrns and {val=val.stuff, ns=attrns.stuff} or val.stuff,
  RECURSION_POINT
} or content.stuff

note that RECURSION_POINT repeats 0 or more times.

E.g. the following MDXML document:

##version
###1.1
##encoding
###utf-8

`This is a list of programming languages and programming language books, in MDXML`

#programming
> #languages
> > #language
> > > #name
> > > > Lua
> > >
> > > #link
> > > > http://www.lua.org/
> >
> > #language
> > > #name
> > > > Python
> > >
> > > #link
> > > > https://www.python.org/
>
> # books
> > #book
> > ##edition
> > ###3
> > > #name
> > > > Programming in Lua
> > >
> > > #ISBN
> > > > 859037985X

Should produce the following table: (The weird table structure is so 
each line matches the equivalent line in the MDXML.)

{ [0] = 'programming',
  { [0] = 'languages',
    { [0] = 'language',
      { [0] = 'name',
        'Lua'
      },
      { [0] = 'link',
        'http://www.lua.org/'
      } },
    { [0] = 'language',
      { [0] = 'name',
        'Python'
        },
      { [0] = 'link',
        'https://www.python.org/'
      } } },
  { [0] = 'books',
    { [0] = 'book',
      ['edition'] =
      '3',
      { [0] = 'name',
        'Programming in Lua'
      },
      { [0] = 'ISBN',
        '859037985X'
      } } } }

And the following MDXML document:

##version
###1.1
##encoding
###utf-8

#root
> #a
> #b
> #c
> stuff

Should produce:

{ [0] = 'root',
  {[0] = 'a'},
  {[0] = 'b'},
  {[0] = 'c'},
  'stuff'
}

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