Fun base system converter

-- done in LuaU, expect compound assignments and exclusive keywords



function FACT_NumToStrFromBase(charstable)
    local base = #charstable
    return function(num)
        local res = ''

        local its = 1 + math.max(0,math.floor(math.log(num,base)))

        for i=its,1,-1  do -- going down number places
            local factor = base ^ (i - 1)

            local nk = base - 1

            for k=base,1,-1 do -- going down the base to 1
                local num2 = factor * (k - 1)

                if num - num2 < 0 then continue end

                nk = k
                num -= num2

                break
            end

            res ..= charstable[nk]
        end

        return res
    end
end

function FACT_StrToNumFromBase(charstable)
    local base = #charstable
    local FlippedCharacters = {}
    for i,v in next,charstable do FlippedCharacters[tostring(v)] = i end

    return function(str)

        local res = 0

        for a=1,#str do -- iterate each letter
            local letter = str:sub(a,a)

            local num = (FlippedCharacters[letter] - 1) * base ^ (#str - a)
            res += num
        end

        return res
    end
end

local numtobin = FACT_NumToStrFromBase(string.split('01',''))
local numtohex = FACT_NumToStrFromBase(string.split('0123456789abcdef',''))

local bintonum = FACT_StrToNumFromBase((string.split('01','')))
local hextonum = FACT_StrToNumFromBase(string.split('0123456789abcdef',''))


for a=0,32 do
    local b = numtobin(a)

    print(a,b,bintonum(b))
end