Lexer for my programming language

local buffer = {} -- stores strings until new line or space 'n shit
--local string = "12+32"
local a_z = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_"
local digits = "1234567890"
local symbols = {"||"}
local operators = {"+","-","/","*","=","#","<",">"} -- operators
local whitespace = {" ","\n","\t","\r"} -- list of whitespaces
local keywords = {
    "var",
    "log", -- print but its a keyword and is shorter than print so it has a higher ranking.
    "pairs",
    "const",
    "and",
    "else",
    "elseif",
    "or",
    "till", -- until is deprecated and unreliable
    "end",
    "function",
    "break",
    "continue",
    "not",
    "false",
    "true",
    "then",
    "while",
    "for",
    "goto", -- we added all lua keywords + some more
    "return",
    "do",
    "in",
    "local"
}
local built_in_functions = {
    "print" -- the same as log
}
--return
function find(f, l) -- find element v of l satisfying f(v)
  for _, v in ipairs(f) do
    if l == v then
        return true
    end
  end
  return false
end

  local module = {}
module = function(data) -- lexer is a module
    local id = 1 -- position in the string; also the id of the token
    local pos = 1 -- position in the string
    local start = 1 -- the start
    local lastnewline = 1 -- the last newline
    local buffer = {} -- complicated stuff rc8s doesnt know
    local lines = {}
    local lex = {}
    local function PushToken(type, value)
        local d = {
            type = type,
            token = value,
            id = id
        }
        table.insert(lex, d)
    end
    local function BufferAdd(v)
        buffer[#buffer + 1] = v -- adds to buffer (long value thing)
    end
  local function clearb()
      buffer = {}
  end
    local function newline()
        lastnewline = pos
        lines[#lines + 1] = buffer
        buffer = {} -- clears buffer
    end
    while pos < #data + 1 and pos ~= #data + 1 do
        local char = data:sub(pos, pos)
        local behind = data:sub(start, pos)
        local behind2 = data:sub(lastnewline, pos)
        if digits:find(char,1,true) then
        clearb()
            --print(char)
            repeat
                BufferAdd(char)
                pos = pos + 1
                char = data:sub(pos,pos)
            until not digits:find(char,1,true) or pos > #data
            PushToken("int", table.concat(buffer))
            buffer = {} -- clears buffer
    elseif find(symbols,char) then
      PushToken("symbol",char)
        pos = pos + 1
        elseif char == "'" or char == '"' and not find(operators,char) then -- activating string
      clearb()
            char = ""
        --print(char)
            repeat
                BufferAdd(char)
                pos = pos + 1
                char = data:sub(pos,pos)
            until char == '"' or char == "'" or pos > #data

            PushToken("string", table.concat(buffer))

            buffer = {} -- clears buffer
        pos = pos + 1
        elseif find(operators,char) then
      clearb()
            repeat
                BufferAdd(char)
                pos = pos + 1
                char = data:sub(pos,pos)
            until not find(operators,char) or pos > #data
            PushToken("operator", table.concat(buffer))
            buffer = {} -- clears buffer
    else
      --print("t")'
        pos = pos + 1
        --local char = data:sub(pos, pos)
      BufferAdd(char)
        --print(table.concat(buffer))
      if find(keywords,table.concat(buffer)) then
          PushToken("keyword",table.concat(buffer))
      elseif find({'~~'},table.concat(buffer)) then -- activation of comment
        --print(char)
        clearb()
          char = ""
          pos = pos - 1
        repeat
                  BufferAdd(char)
                  pos = pos + 1
          char = data:sub(pos,pos)
              until char == "\n" or char == "" or pos > #data
        PushToken("comment",table.concat(buffer))
    elseif find(built_in_functions,table.concat(buffer)) then
        PushToken("Built_in_function",table.concat(buffer))

      end
      --pos = pos + 1

        end
    --if pos == #data or pos > #data then break end

    end
  return lex

end
return module