Re: Ada.Numerics.Big_Numbers.Big_Integer has a limit of 300 digits?

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 2021-12-22 21:26, Mark Lorenzen wrote:
> On Wednesday, December 22, 2021 at 6:27:57 PM UTC+1, Michael Ferguson
> wrote:
>> On Wednesday, December 22, 2021 at 11:02:03 AM UTC-6, Luke A. Guest
>> wrote:
>>> On 22/12/2021 05:57, Michael Ferguson wrote:
>>>> I just started using the Big_Integer library that is a part of
>>>> the 202X version of ADA.
>>>> 
>>>> It is repeatedly described as an "arbitrary precision library"
>>>> that has user defined implementation.
>>>> 
>>>> I was under the impression that this library would be able to
>>>> infinitely calculate numbers of any length, but there is
>>>> clearly a default limit of 300 digits.
>>> What are you doing that requires that number of digits?
>> I am working on ProjectEuler.net problem number 48.
>> 
>> The questions asks you to sum the numbers n^n for (2 <= n <= 1000)
>> and determine what the last ten digits of this number are.
> 
> Interesting. Assume that the problem is related to the maximum size
> of lexical elements, can't you then use the "rem" function from
> Big_Integers to determine the last 10 digits e.g. by something like
> this Last_10_Digits = My_Very_Large_Number rem To_Big_Integer(1) **
> 10?


You no doubt meant To_Big_Integer (10), not To_Big_Integer(1).

But it should be possible to write directly "... rem 10_000_000_000", 
and even if that constant is too large for the Integer type, because 
Big_Integer has the Integer_Literal aspect (assuming GNAT already 
implements it).