Module:If in category

Due to a server limit of 500 "expensive parser function" calls (e.g. #ifexist:, PAGESIZE:, and PAGESINCATEGORY:), this module will only work properly if the page using it has not already exceeded the limit. When the limit is exceeded, the page using this template or module is categorised in Category:Pages with too many expensive parser function calls. (further information)

This module implements {{if in category}}

Usage

{{if in category | [category] | [result if true] | [result if false] | page = [page] }}

If |page= is omitted, the current page is used. If both the second and third unnamed parameters are omitted, the second unnamed parameter defaults to yes.

local p = {}
local TableTools = require('Module:TableTools')

function p.main(frame)
	local getArgs = require('Module:Arguments').getArgs
	local args = getArgs(frame)
	return p._main(args)
end

function p._main(args)
	-- create a title object
	local page =  mw.title.new((args.page or '')) or mw.title.getCurrentTitle()
	if TableTools.inArray(page.categories, string.gsub( args[1], '^[Cc]ategory:', '' )) then
		if not args[3] then
		-- if we are are not given anything to return, return 'yes' if it evalulates to true
    		return args[2] or 'yes'
    	else 
    		return args[2]
		end
	else
		return args[3]
	end
end

return p