Re: Need lpeg hint

[Martin Kortmann <mail@...>]

Am 13.08.2011 um 21:36 schrieb Peter Cawley:

> On Sat, Aug 13, 2011 at 8:18 PM, Martin Kortmann <mail@kortmann.de> wrote:
>> Hello all,
>> 
>> I'm trying to learn the usage of lpeg and i need a push to the right direction on the following problem:
>> 
>> I will parse files with the following structure:
>> 
>> blockname1 {
>>  key1 value1
>>  key2 value2
>>  blockname2 {
>>    key3 value3
>>    blockname3 {
>>      key4 value4
>>    }
>>    key5 value5
>>  }
>> }
>> 
>> there are named blocks of datas, the datas are several key/value pairs or other named blocks of datas. Seem simple, but i don't get a right grammar for this syntax.
>> Can someone give me a start for this?
>> 
>> Thanks Martin
> 
> Very quickly thrown together, but seems to work for your example:
> http://codepad.org/z49J4o8z
> 


Thank you Peter, this seems to work. but why does the following code not work?

local L = require "lpeg"

local function makepairs(kvkv_array)
  local t = {}
  for i = 1, #kvkv_array, 2 do
    t[kvkv_array[i]] = kvkv_array[i+1]
  end
  return t
end

local ws = L.S" \r\n\t"^0 -- whitespace
local id = L.C(L.R("az","AZ","09")^1) -- identifiers
local value = id -- values (currently same as identifiers)

local grammar = L.P { "block",

	entry = ws * id * ws * value + L.V('block'), -- key value OR block

	block = ws * id * ws * "{" * (L.Ct(L.V"entry"^0) / makepairs) * ws * "}" / function(k, v) return {[k] = v} end;

}

local result = grammar:match[[

blockname1 {
 key1 value1
 key2 value2
 blockname2 {
   key3 value3
   blockname3 {
     key4 value4
   }
   key5 value5
 }
}

]]


Martin