-- Patrick Hurd
-- Flattens an arbitrary nesting of arrays
-- Runs using Lua5.3
-- March 26, 2017

-- I first wrote this in Perl, then remembered Perl does automatic
-- list flattening. Next I started writing it in Golang until I
-- realized Golang doesn't let you arbitrarily nest arrays.
-- Lua might be the only language I know which allows arbitray
-- nesting.

--[[
Takes a Lua table as an argument, then recurses on each nested
table. Returns a flattened Lua table.
]]--
function flatten(array)
	local ret = {}
	for k,v in pairs(array) do
		-- If the element is a nested array
		if type(array[k]) == "table" then
			-- Recurse on nested array
			local flattened = flatten(array[k])
			for i,j in pairs(flattened) do
				table.insert(ret, j)
			end
		else
			table.insert(ret, v)
		end
	end
	return ret
end

--[[
This is just a helper function to format the arrays as they
appear in memory - with nesting.
]]--
function parsed(array)
	local ret = "{"
	for k,v in pairs(array) do
		-- If the element is a nested array
		if type(array[k]) == "table" then
			-- Recurse on nested array
			local flattened = parsed(array[k])
			ret = ret .. flattened
		else
			ret = ret .. v
		end
		if k < #array then
			ret = ret .. ", "
		end
	end
	ret = ret .. "}"
	return ret
end

-- Tests
test1 = {1, 2, {3, 4, {5}, 6}}
print("Test 1:")
print(parsed(test1))
print(parsed(flatten(test1)))

print()

test2 = {{{1, 2}, 3, 4}, 5, 6, {7, 8}, 9, 10}
print("Test 2:")
print(parsed(test2))
print(parsed(flatten(test2)))