-- Helpers for queries using transitive properties  local p = {} local wd = require "Module:Wikidata" local tools = require "Module:Wikidata/Outils"  local function getids(item, query)  	query.excludespecial = true 	query.displayformat = 'raw' 	query.entity = item 	return wd.stringTable(query) end   -- add new items to a list, avoiding duplicates local function addnewvalues(olditems, newitems, maxnum, stopval) 	if not newitems then 		return olditems 	end 	for _, qid in pairs(newitems) do 		if stopval and (qid == stopval) then 			table.insert(olditems, qid) 			return olditems 		end 		if maxnum and (#olditems >= maxnum) then 			return olditems 		end 		if not tools.isHere(olditems, qid) then 			table.insert(olditems, qid) 		end 	end 	return olditems end  -- recursively adds a list of qid to an existing list, based on the results of a query function p.addVals(list, query, maxdepth, maxnodes, stopval) 	maxdepth = maxdepth or 10 	maxnodes = maxnodes or 100 	if (maxdepth < 0) then 		return list 	end 	if stopval and tools.isHere(list, stopval) then 		return list 	end 	local origsize = #list 	for i = 1, origsize do 		-- tried a  "checkpos" param instead of starting to 1 each time, but no impact on performance 		local candidates = getids(list[i], query) 		list = addnewvalues(list, candidates, maxnodes, stopval) 		if list[#list] == stopval then 			return list 		end 		if #list >= maxnodes then 			return list 		end 	end 	if (#list == origsize) then 		return list 	end 	return p.addVals(list, query, maxdepth - 1, maxnodes, stopval, origsize + 1) end  -- returns a list of items transitively matching a query (orig item is not included in the list) function p.transitiveVals(item, query, maxdepth, maxnodes, stopval) 	maxdepth = maxdepth or 10 	local vals = getids(item, query) 	if not vals then 		return nil 	end 	return p.addVals(vals, query, maxdepth - 1, maxnodes, stopval) end  -- returns true if an item is the value of a query, transitively function p.inTransitiveVals(searchedval, sourceval, query, maxdepth, maxnodes ) 	local vals = p.transitiveVals(sourceval, query, maxdepth, maxnodes, searchedval ) 	if vals and vals[#vals] == searchedval then 		return true 	end 	return false end  -- returns true if an item is a superclass of another, based on P279 function p.isSubclass(class, item, maxdepth) 	local query = {property = 'P279'} 	if class == item then -- item is a subclass of itself iff it is a class 		if getids(item, query) then 			return true 		end 		return false 	end 	return p.inTransitiveVals(class, item, query, maxdepth ) end  -- returns true if one of the best ranked P31 values of an item is the target or a subclass of the target -- rank = 'valid' would seem to make sense, but it would need to check for date qualifiers as some P31 values have begin or end date function p.isInstance(targetclass, item, maxdepth) 	maxdepth = maxdepth or 10 	local directclasses = p.transitiveVals(item, {property = 'P31'}, 1) 	if not directclasses then 		return false 	end 	for i, class in pairs(directclasses) do 		if p.isSubclass(targetclass, class, maxdepth - 1) then 			return true 		end 	end 	return false end  return p