-- This module finds the highest existing archive number for a set of talk -- archive pages.  local expSearch = require('Module:Exponential search') local p = {}  local function raiseStartNumberError(start)  error(string.format(  'Invalid start number "%s" supplied to [[Module:Highest archive number]] (must be an integer)',  tostring(start)  ), 3) end  local function pageExists(page)  local success, exists = pcall(function()  return mw.title.new(page).exists  end)  return success and exists end  function p._main(prefix, start)  -- Check our inputs  if type(prefix) ~= 'string' or not prefix:find('%S') then  error('No prefix supplied to [[Module:Highest archive number]]', 2)  end  if start ~= nil and (type(start) ~= "number" or math.floor(start) ~= start) then  raiseStartNumberError(start)  end  start = start or 1   -- Do an exponential search for the highest archive number  local result = expSearch(function (i)  local archiveNumber = i + start - 1  local page = prefix .. tostring(archiveNumber)  return pageExists(page)  end, 10)   if result == nil then  -- We didn't find any archives for our prefix + start number  return nil  else  -- We found the highest archive, but the number is always 1-based, so  -- adjust it for our start number  return result + start - 1  end end  function p.main(frame)  local args = require('Module:Arguments').getArgs(frame, {  trim = false,  removeBlanks = false,  wrappers = 'Template:Highest archive number'  })  local prefix = args[1]   -- Get the start archive number, if specified.  local start = args.start  if start == "" then  start = nil  elseif start then  start = tonumber(start)  if not start then  raiseStartNumberError(args.start)  end  end   return p._main(prefix, start) end  return p