Lazy streams with coroutines

demhydraz-lazy.lua

local function pull(c)
	if coroutine.status(c) == 'dead' then
		return false
	else
		local ok, res = coroutine.resume(c)
		if coroutine.status(c) == 'dead' then
			return false
		elseif ok then
			return true, res
		else
			error(res)
		end
	end
end

local function printS(c)
	while true do
		local ok, v = pull(c)
		if ok then
			print(v)
		else
			break
		end
	end
end

local function fromList(l)
	return coroutine.create(function()
		for _, v in ipairs(l) do
			coroutine.yield(v)
		end
	end)
end

local function init(c)
	return coroutine.create(function()
		local ok, v1 = pull(c)
		while true do
			local ok, v2 = pull(c)
			if ok then
				coroutine.yield(v1)
				v1 = v2
			else
				break
			end
		end
	end)
end

printS(init(fromList({1, 2, 3, 4, 5})))