num_transform.lua -- number manipulation library

local lib
lib = {
    digitsToNum = function(digits, base)
        local num, k = 0, 1
        for i = #digits, 1, -1 do
            if digits[i] >= base then
                error("\number transfromation error: could not transfrom number "
                ..tostring(digits[i]).." to base "..tostring(base))
            end
            num = num + digits[i] * k
            k = k * base
        end
        return num
    end
   ,getNumberLength = function(num, base)
        if num == 0 then return 0 end
        if num < 0 then num = -num end
        return math.floor(math.log(num) / math.log(base)) + 1
    end
   ,toBase = function(num, base, forcedLength)
        local length, t = lib.getNumberLength(num, base), {}
        if forcedLength ~= nil then
            for i = 1, forcedLength do t[i] = 0 end
        end
        local l = math.max(forcedLength or 0, length)
        for i = 1, length do
            local v = num % base
            t[l - i + 1] = v
            --if num < base then break end
            num = math.floor(num / base)
        end
        return t
    end
}
return lib