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From: Qun-Ying <zhu.qunying@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: getting same output as gfortran, long_float
Date: Thu, 30 Apr 2015 15:27:43 -0700
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Date: 2015-04-30T15:27:43-07:00
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Currently, on my x86_64 Linux with GCC 4.9.2, the maximum digits I could 
define is 18:
type My_float is digits 18;

Far less then what you would expected.

You would need to use some bindings to MPFR/GMP library for more precisions.

Jeffrey R. Carter wrote:
> On 04/30/2015 02:17 PM, Nasser M. Abbasi wrote:
>>
>> with ada.text_io; use ada.text_io;
>> procedure foo_2 is
>>    x : Long_Long_Float;
>> begin
>>    x := 12.0 * 0.0001/(1.0 * (1.0 - 0.1)**4 );
>>    put_line(Long_Long_Float'image(x));
>> end foo_2;
>
> What do you get with this:
>
> With Ada.Text_IO;
> procedure Foo_However_Many is
>     X : constant := 12.0 * 0.0001 / (1.0 * (1.0 - 0.1) ** 4);
> begin -- Foo_However_Many
>     Ada.Text_IO.Put_Line (Item => X'Img);
> end Foo_However_Many;
>
> ? You probably can't get any more significant digits from GNAT than this gives
> you. You could also try a type defined as
>
> type Big is digits System.Max_Digits;
>