Does lpeg.B(-n) has any real meaning ?
I did a patch that use B(-n) for the behind n instruction
NOTE: %b == lpge.B(-1) == behind 1
Example: lua patten "(.*)and(.*)"
pat = re.compile "{(g <- 'and' / . [^a]* g)+ %b%b%b} ... {.*}"
= pat:match 'this and that and whatever'
this and that
whatever
Example: capture chars in groups of 3's
pat = re.compile "({...} %b%b)+"
= pat:match "123456789"
123 234 345 456 567 678 789
----
Follwing is the patches if anyone interested (ONLY 4 lines !)
>diff lpeg\lptree.c lpeg-1.0.1\lptree.c
430d429
< tree->u.n = n; // TNot, possibly UNDO
689d687
< if (sib1(tree)->tag == TNot) n = sib1(tree)->u.n;
>diff lpeg\lpcode.c lpeg-1.0.1\lpcode.c
661d661
< if (sib1(tree)->tag != TNot) // TNot == UNDO
>diff lpeg\re.lua lpeg-1.0.1\re.lua
23c27,28
< local Predef = { nl = m.P"\n", b = m.B(-1) }
---
> local Predef = { nl = m.P"\n" }
