lpegrex grammar

[mingodad]

Would be nice to have a lpegrex grammar parser as example, I've got this one grammar so far:

-- lpegrex in lpeg
pattern         <- exp !.
exp             <- S (grammar / alternative)

alternative     <- seq ('/' S seq)*
seq             <- prefix*
prefix          <- '&' S prefix / '!' S prefix / suffix
suffix          <- primary S (([+*?] S
                            / '^' (
				[-+]? num  -- (exactly n / at (least / most) n repetitions
				/ '^' name -- Syntax of relabel module. The pattern p^l is equivalent to p + lpeglabel.T(l).
				)
                            / '->' S (string / pcap / name / num)  -- capture
                            / '=>' S name) S)* -- match time capture

primary         <- '(' exp  ')' S / string / keyword / class / defined
                 / '{:' (name ':')? exp ':}' S  -- (named or anonymous) group capture
                 / '=' name           -- back reference
                 / '@' exp   -- for throwing labels errors on failure of expected matches
                 / pcap
                 / '{~' exp '~}' S  -- substitution capture
                 / '{|' exp '|}' S  -- table capture
                 / '{' exp '}' S    -- simple capture
		 / '~?' S             -- optional capture
		 / '~>' S ( 'foldleft' / 'foldright' / 'rfoldleft' / 'rfoldright' / name ) S -- fold capture
		 / '$' (string / name / num / pcap)
                 / '.' S
                 / name S !(asttag / arrow )
                 / '<' S name '>' S    -- old-style non terminals
		 / '%{' S name '}' S   -- Syntax of relabel module. Equivalent to lpeglabel.T(l)

grammar         <- definition+
definition      <- name S asttag? arrow exp

class           <- '[' '^'? item (!']' item)* ']' S
item            <- defined / range / .
range           <- . '-' [^]]

S               <- (%s / '--' [^%nl]*)*   -- spaces and comments
name            <- [A-Za-z_]([A-Za-z0-9_] / '-' !'>' )* S
arrow           <- (  '<--'    -- rule
                    / '<=='    -- for rules that capture AST Nodes
		    / '<-|'    -- for rules that capture tables
		    / '<-'
		    ) S
num             <- [0-9]+ S
string          <- ('"' [^"]* '"' / "'" [^']* "'") S
defined         <- '%' name  -- pattern defs[name] or a pre-defined pattern
keyword         <- '`' [^`]+ '`' S  -- tokens/keywords with automatic skipping
asttag          <- ':' S name  -- Capture tagged node rule
pcap            <- '{}' S -- position capture

But it doesn't do any capture to genereate an AST.

Can someone help finish it ?