adventofcode-2021/utils.lua

function split(text, sep)
	local parts = {}
	local start = 0
	local from, to = text:find(sep)
	while from ~= nil do
		table.insert(parts, text:sub(start, from - 1))
		text = text:sub(to + 1)
		from, to = text:find(sep)
	end
	table.insert(parts, text)
	return parts
end

function sign(n)
	if n == 0 then return 0
	elseif n < 0 then return -1
	else return 1
	end
end

function foreach(t, f)
	for k, v in pairs(t) do
		t[k] = f(v)
	end
end

function printtable(t, nonewline)
	for k, v in pairs(t) do
		io.write(k..":")
		if type(v) == "table" then
			io.write("(")
			printtable(v, true)
			io.write(") ")
		else
			io.write(tostring(v).." ")
		end
	end
	if not nonewline then
		io.write("\n")
	end
end

function count(t, pred)
	local count = 0
	for k, v in pairs(t) do
		if pred(v) then count = count + 1 end
	end
	return count
end

function foldl(t, f, a)
	for k, v in pairs(t) do
		a = f(a, v)
	end
	return a
end

function sum(t)
	return foldl(t, function (x, y) return x + y end, 0)
end

function char(s, index)
	return string.char(string.byte(s, index))
end

function chars(s)
	local index = 0
	return function()
		if index < #s then
			index = index + 1
			return char(s, index)
		else
			return nil
		end
	end
end

function bin2dec(str)
	local v = 0
	for c in chars(str) do
		v = v * 2
		if c == "1" then v = v + 1 end
	end
	return v
end

function euler(n)
	return n * (n + 1) / 2
end