sql.lp
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	#begin_lua
	local n = 0
	local env = luasql.sqlite3()
	local conn = env:connect("test.sqlite3")
	conn:execute("CREATE TABLE IF NOT EXISTS test (x, y)")
	conn:execute("CREATE UNIQUE INDEX IF NOT EXISTS \
	test_index ON test (x, y)")

	function query()
	local cur = conn:execute("SELECT * FROM test")
	local res = {}
	while true do
	local row = {}
	row = cur:fetch(row, "n")
	if row == nil then break end
	res[#res + 1] = Val.new(Val.FUNC, row)
	end
	cur:close()
	return res
	end

	function insert(name)
	Assignment.begin(name, 2)
	while Assignment.next() do
	if Assignment.isTrue() then
	local x = Assignment.args()[1]
	local y = Assignment.args()[2]
	local res = conn:execute("INSERT INTO test \
	VALUES(" .. x .. "," .. y .. ")")
	if res ~= nil then n = n + 1 end
	end
	end
	end

	function onBeginStep() insert("p") end
	function onModel() insert("q") end
	function onEndStep() print("inserted " .. n .. " values") end

	#end_lua.

	p(1,1).
	p(X+1,Y) :- (X,Y) := @query().
	#odd { q(X,Y+1) : p(X,Y) }.