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From: "REH" <spamjunk@stny.rr.com>
Newsgroups: comp.lang.ada
Subject: Re: where exactly c++,c fail and Ada gets thru'
Date: 27 Apr 2006 09:48:08 -0700
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Date: 2006-04-27T09:48:08-07:00
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Martin Krischik wrote:
> Maciej Sobczak wrote:
>
> > Yes, classes are used to define new types. Is there any problem with
> > this? It is also necessary in Ada if we want to do just a bit more of
> > what is provided by type and subtype constructs.
>
> Say:
>
> type Y_Type is range 1 .. 10;
> subtype X_Type is new x range 1 .. 5;
>
> function F (X: X_Type) return Y_Type is
> begin
>   return X + 3;
> end F
>
> Now I would expect that an Ada compiler will not insert any runtime checks
> as X + 3 is allways in the range of Y_Type. However:
>
> function G (X: X_Type) return Y_Type is
> begin
>   return X + 7;
> end G;
>
> may well be outside the range of Y_Type and if so CONSTRAINT_ERROR will be
> raised.
>
> Now say we have a suitable C++ range template:
>
> typedef range<int, 1, 10> Y_Type;
> typedef range<Y_Type, 1, 5> X_Type;
>
> Y_Type F (X_Type X)
>   {
>   return X + 3;
>   }
>
> Y_Type G (X_Type X)
>   {
>   return X + 7;
>   }
>
> Now anyone up to the challenge to define:
>
> template <typename Base_Type, Base_Type First, Base_Type Last>
> range::operator = (Base_Type right)
>
> template <typename Base_Type, Base_Type First, Base_Type Last>
> range::operator + (Base_Type right)
>
> template <typename Base_Type, Base_Type First, Base_Type Last>
> range::range (Base_Type right)
>
> in such a way that it works like Ada - inclusive the *realistic* change that
> the compiler will optimize away the range check in F ().

I have done this.