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From: Shark8 <onewingedshark@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Efficiency of code generated by Ada compilers
Date: Tue, 10 Aug 2010 07:28:27 -0700 (PDT)
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Date: 2010-08-10T07:28:27-07:00
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On Aug 10, 7:52 am, Elias Salom=E3o Helou Neto <eshn...@gmail.com>
wrote:

> > function Generic_Elliptic_Integral (X : Real; K : Real) return Real is
> >    type Internal is digits Real'Digits * 2;  -- You cannot do that!
> > begin
> >    ...
>
> I don't fully understand the code, but it does seem to be very
> intuitive. What does
>
>   type Real is digits <>;
>
> mean? Is "digits" a keyword of the language? I guess Ada groups
> fundamental types in categories and "digits" mean we must use some
> floating point type as the template argument, right? It sounds like a
> good idea, specially if things like that could be done for user
> defined types, i.e., if I can define my own type that "is digits <>".
>
> > --
> > Regards,
> > Dmitry A. Kazakovhttp://www.dmitry-kazakov.de
>
>

"Digits" is a keyword in the language, in particular it is used to
define the number of digits-of-precision in a floating-point type. The
<> in this case is telling the compiler that the type 'Real', which is
the name some floating-point type will be referred to in the generic;
the purpose is to allow the programmer the ability to write code that
is independent of the precision but dependent on the [properties of
the] class of type.