local lpeg = require "listlpeg"
local p = lpeg.P{
"patt",
_one_ = lpeg.C(lpeg.L(lpeg.L"one")),
patt = (lpeg.V"one" + lpeg.L(lpeg.V"patt") + lpeg.P(1))^0
}
print(p:match{ "something", { "something", { "one" } } }[1]) -- one
----
The "listre" syntax is easier on the eyes:
----
local re = require "listre"
local p2 = re.compile[[
patt <- (<<one>> / { <patt> } / .)*
one <- { "one" }
]]
----
Fetch and compile listlpeg again to run this example, the verifier had a bug where it would detect a spurious left recursion in patt. test/list.lua has more interesting search examples.
--
Fabio Mascarenhas
On Sat, Mar 27, 2010 at 5:05 PM, Wesley Smith
<wesley.hoke@gmail.com> wrote:
I'm testing out some ideas using lpeg-list and was wondering how one
could express a recursive search through nested tables. Using lpeg to
search through a string is pretty straightforward using
(patt + P(1))^0
This works equally well for lists, but doesn't work at all for nested
lists. For example, I was trying to see how to generalize this
pattern:
local patt = L"one" * L(L"one" * L(L"one"))
It matches this:
local code = {"one", {"one", {"one"}, }, }
Now let's say I have:
local code = {"something", {"something", {"one"}, }, }
How can I express a recursive search through nested tables to find the
list containing "one"? My first attempt was:
(patt + L( (patt + P(1))^1 ) + P(1))^0
This only goes one level deep and I need it to exhaustively recurse.
Any ideas on how to do this?
thanks,
wes
