-- This module may be used to compare the arguments passed to the parent -- with a list of arguments, returning a specified result if an argument is -- not on the list  require ('strict');  local p = {}  local function trim(s) 	return s:match('^%s*(.-)%s*$') end  local function isnotempty(s) 	return s and s:match('%S') end  local function clean(text) 	-- Return text cleaned for display and truncated if too long. 	-- Strip markers are replaced with dummy text representing the original wikitext. 	local pos, truncated 	local function truncate(text) 		if truncated then 			return 		end 		if mw.ustring.len(text) > 25 then 			truncated = true 			text = mw.ustring.sub(text, 1, 25) .. '...' 		end 		return mw.text.nowiki(text) 	end 	local parts = {} 	for before, tag, remainder in text:gmatch('([^\127]*)\127[^\127]*%-(%l+)%-[^\127]*\127()') do 		pos = remainder 		table.insert(parts, truncate(before) .. '<' .. tag .. '>...</' .. tag .. '>') 	end 	table.insert(parts, truncate(text:sub(pos or 1))) 	return table.concat(parts) end  function p._check(args, pargs) 	if type(args) ~= "table" or type(pargs) ~= "table" then 		-- TODO: error handling 		return 	end  	-- create the list of known args, regular expressions, and the return string 	local knownargs = {} 	local regexps = {} 	for k, v in pairs(args) do 		if type(k) == 'number' then 			v = trim(v) 			knownargs[v] = 1 		elseif k:find('^regexp[1-9][0-9]*$') then 			table.insert(regexps, '^' .. v .. '$') 		end 	end  	-- loop over the parent args, and make sure they are on the list 	local ignoreblank = isnotempty(args['ignoreblank']) 	local showblankpos = isnotempty(args['showblankpositional']) 	local values = {} 	for k, v in pairs(pargs) do 		if type(k) == 'string' and knownargs[k] == nil then 			local knownflag = false 			for _, regexp in ipairs(regexps) do 				if mw.ustring.match(k, regexp) then 					knownflag = true 					break 				end 			end 			if not knownflag and ( not ignoreblank or isnotempty(v) )  then 				table.insert(values, clean(k)) 			end 		elseif type(k) == 'number' and knownargs[tostring(k)] == nil then 			local knownflag = false 			for _, regexp in ipairs(regexps) do 				if mw.ustring.match(tostring(k), regexp) then 					knownflag = true 					break 				end 			end 			if not knownflag and ( showblankpos or isnotempty(v) ) then 				table.insert(values, k .. ' = ' .. clean(v)) 			end 		end 	end  	-- add results to the output tables 	local res = {} 	if #values > 0 then 		local unknown_text = args['unknown'] or 'Found _VALUE_, '  		if mw.getCurrentFrame():preprocess( "" ) == "" then 			local preview_text = args['preview'] 			if isnotempty(preview_text) then 				preview_text = require('Module:If preview')._warning({preview_text}) 			elseif preview_text == nil then 				preview_text = unknown_text 			end 			unknown_text = preview_text 		end 		for _, v in pairs(values) do 			-- Fix odd bug for | = which gets stripped to the empty string and 			-- breaks category links 			if v ==  then v = ' ' end  			-- avoid error with v = 'example%2' ("invalid capture index") 			local r = unknown_text:gsub('_VALUE_', {_VALUE_ = v}) 			table.insert(res, r) 		end 	end  	return table.concat(res) end  function p.check(frame) 	local args = frame.args 	local pargs = frame:getParent().args 	return p._check(args, pargs) end  return p