Re: LPeg back captures

[Andrew Starks <andrew.starks@...>]

On Wed, Oct 23, 2013 at 10:55 PM, Andrew Starks <andrew.starks@trms.com> wrote:
> On Wed, Oct 23, 2013 at 10:10 PM, Sean Conner <sean@conman.org> wrote:
>>> >         DIGIT        = R"09"
>>> >         delim_char   = P"!" -- Cb("delim")
>>> >         flags        = P"i"
>>> >         backref      = P"\\" * DIGIT
>>> >         escapeddelim = P"\\" * delim_char
>>> >         anychar      = P(1) - delim_char
>>> >         string       = (escapeddelim + anychar)^1
>>> >         repl         = C((string + backref)^0)
>>> >         ere          = C((P(1) - delim_char)^0)
>>> >         idelim_char  = Cg(P"/" + P"!" + (P(1) - (DIGIT + flags)),"delim")
>>> >         regexp       = Ct(
>>> >                             idelim_char
>>> >                             * Cg(ere,"re")
>>> >                             * delim_char
>>> >                             * Cg(repl,"replace")
>>> >                             * delim_char
>>> >                             * Cg(flags^0,"flags")
>>> >                          )
>
> Man... I'm sorry. I thought I was pretty sure on this. I did some
> tests on a simpler example and I was wrong again. Order of declaration
> doesn't matter....
>
>
> ```
> lpeg = require'lpeg'
>
> P, Cg, Cb, C = lpeg.P, lpeg.Cg, lpeg.Cb, lpeg.C
>
> the_forb_back_there = Cb("forb")
> forb_cap = Cg(P(P"foo" + "bar"), "forb")
>
> main_patt = C(forb_cap * (P(1))^1 * the_forb_back_there)
>
> print(main_patt:match("barnillydissle"))
> -->barnillydissle bar
> ```
>
> bar is coming out as a separate return value.... I think that may be
> the problem. I'm gonna dig more.


I'm gonna work on a solution, but at least I think I know the problem:

Cb doesn't work on nested captures. So your other statements (ere,
escapeddelim, etc) are "out of scope" with delim_char.

-Andrew