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From: "jimmaureenrogers@worldnet.att.net" <jimmaureenrogers@worldnet.att.net>
Newsgroups: comp.lang.ada
Subject: Re: why learn C?
Date: 2 Apr 2007 19:58:55 -0700
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Date: 2007-04-02T19:58:55-07:00
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On Apr 2, 2:13 am, "kevin  cline" <kevin.cl...@gmail.com> wrote:
> On Mar 30, 9:41 pm, "jimmaureenrog...@worldnet.att.net"  For instance:
> > No, run time checks are needed for things that cannot be checked at
> > compile time. Ada helps is more helpful with run time checks than is
> > C or C++ due to the automated check writing built by the compilers.
> > For instance, if you define an integer type with a valid range of
> > values from -10 to 10, the compiler will perform all necessary
> > range checking for that type.
>
> > type My_Int is range -10..10;
>
> That's perfect if it happens to be the exact thing that you need.  It
> doesn't help much if what you need is a point inside the unit circle.
>

That is an interesting non-sequiter. No integer type would be
satisfactory to define a point within a unit circle.

> In C++ the language provides neither of these things, but they are
> both be implemented in a few lines of code.
>
> In Ada, the implementation of the constrained point is not so
> obvious.

You want a type for specification of a point within a unit circle.
Is this really hard to comprehend:

type Unit_Radius_Type is digits 15 range 0.0..1.0;
type Angle is digits 15 range 0.0..2.0 * Pi;

type Circular_Point is record
   X     : Unit_Radius_Type;
   Theta : Angle;
end record;

Given any unit circle with a known center coordinate, all
points can be designated within 15 digits of accuracy.

Please demonstrate how you would use C++ templates to
create an equivalent definition. I am most curious about the
range-specified and precision-specified floating point types.

Jim Rogers