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Newsgroups: comp.lang.ada
Subject: Re: why learn C?
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From: Markus E Leypold
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Date: Thu, 12 Apr 2007 18:18:36 +0200
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Hyman Rosen <hyrosen@mail.com> writes:

> jimmaureenrogers@worldnet.att.net wrote:
>> I discovered that C++ template language does not allow the
>> specification of a floating point value as a template parameter.
>
> In C++, instantiations are considered the same if their
> parameters are the same, and the standards committee did
> not want the burden of defining T<3.0*(1.0/3.0)> vis a vis
> T<1.0>.

We have been through that discussion before. IMHO that this decision
was even necessarry indicates (in my eyes) the inferiority of the
automatic instantion approach. In C++ the "identity" of an instance
needs to be determined by the parameters. In Ada (and many other
languages with functors) by the act of instantiation.

>
>> one cannot write a C++ template to handle range-specified
>  > floating point classes.
>
> Of course this is wrong. Every floating point number that you
> write in a program is in fact a rational number, and therefore
> depending on the purpose those numbers will have in the template,
> they be represented using small sets of integers in a variety of
> ways. The template itself can then assemble these parts into a
> floating-point constant and use it. Or if that's too burdensome,
> references to floating-point variables are permitted, so getting
> what you want looks rather like Ada generic instantiation.

Groan. How ugly.

Regards -- Markus