A JSON parser in LPeg.re

raj.lua

re = require "re"

local function condense(keyvals)
   local obj = {}
   for i = 1, #keyvals do
      obj[keyvals[i][1]] = keyvals[i][2]
   end 
   return obj 
end

--Nulls are represented by this function. It should work, I guess?
local function null() return nil end 

return re.compile([[
value <- object / array / string / number / word

object <- {| '{' ws (keyval (ws ',' ws keyval)*)? ws '}' |} -> condense
keyval <- {| key ws ':' ws value |}
key <- string

array <- {| '[' ws (value (ws ',' ws value)*)? ws ']' |}

string <- '"' ({| (eseq / char) * |} -> concat) '"'
eseq <- '\' {.}
char <- {[^"]}

number <- { '-'? ((istr ('.' istr? ('e+' istr)?)?) / ('.' istr)) } -> numval
istr <- %d+

word <- { "true" / "false" / "null" } -> wordval

ws <- (%s / %nl)*
]], {
   condense = condense
  ,wordval = {["true"] = true, ["false"] = false, null = null}
  ,numval = tonumber
  ,concat = table.concat
} )