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

[Michael Ferguson <michaelblakeferguson@gmail.com>]

On Wednesday, December 22, 2021 at 11:48:46 AM UTC-6, Niklas Holsti wrote:
> On 2021-12-22 19:27, 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.
> Surely not "user defined"? Possibly "implementation defined".
> >>> I was under the impression that this library would be able to 
> >>> infinitely calculate numbers of any length,
> I have the same impression (up to Storage_Error, of course).
> >> 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. 
> > 
> > Obviously, this is quite a trivial problem when using any arbitrary 
> > precision library. 
> > 
> > I had incorrectly determined that 700^700 had 300 digits, in fact 
> > 700^700 = 3.7E1991. 
> > 
> > However, my code strictly breaks when the loop range is set to 683, 
> > which 683^683 = 8.12E1935.
> How does it break? Some exception, or something else? 
> 
> Mark Lorenzen suggested in an earlier post that the limit might be in 
> the Big_Integer'Image function. The package 
> Ada.Numerics.Big_Numbers.Big_Integers has some other output operations 
> that you could try: 
> 
> function To_String (Arg : Valid_Big_Integer; ...) return String; 
> 
> procedure Put_Image (Buffer : ... ; Arg: in Valid_Big_Integer); 
> 
> Of course those might be internally linked to the 'Image function and 
> have the same possible limitation.

Not 100% sure what modular types are but I did try to do something like the following

subtype VeryBigInteger is Big_Integer range 0 .. 10E10000;

which gave "error: incorrect constraint for this kind of type"

Niklas also gave me an epiphany as the exact error my program gives for the upper limit is

raised STORAGE_ERROR : Ada.Numerics.Big_Numbers.Big_Integers.Bignums.Normalize: big integer limit exceeded

I had thought that since the end of this error said big integer limit exceeded it was a problem with the library, but now I'm starting to think I need to get GNAT to allocated more memory for the program.