Re: ada vs. cpp

["Mike Mohr" <nospam@nowhere.com>]

"Robert*@" <Robert_member@newsguy.com> wrote in message
news:9psrqv016j9@drn.newsguy.com...
> In article <dFlw7.173483$w7.26404906@news02.optonline.net>, "Mike says...
> >
>
> >
> >> There is nothing equivelant in C++ to declaring a new type integer
> >> with restricted range. It is simply not in the C++ language.
> >

Your original reply didn't say anything about type checking,
your original reply objected to the fact that the ranges were
hardcoded so I responded with that in mind.

I fixed the exact problem you cited.

  "The difference is that in Ada the range itself is a separate type
declaration.
   So, one can change the range type in one place and have it propgate all
   over. With your attempt, you hardcoded the range using magic numbers in
   the variable declaration itself, so if the same range is to be used
   somewhere else in the code, or in different variable declaration, you
   need to type it there too manually."

In my response, I have shown how to "change the range in one place
and have it propagate all over." yet in the popular style of this newsgroup
you have added additional requirements to the problem only after I
have presented a complete answer to the original problem :)

> In ada, when you declare a type of a restricted range, the compiler and
run-time
> will check that variables of such type can have values in that range only.
>

      subtype Code is Positive range 1 .. 4;
      subtype Arg  is Positive range 6 .. 8;

      V2 : constant String := V1 (Arg) & '-' & V1 (Code);

By all accounts I am a new Ada programmer, so I am a little confused
by the syntax.  It isn't clear to me how Code, and Arg function in the
expression.

Do strings effectively have a ( ) operator which takes a range as an
argument?

I read V1 (Arg) as V1.substring(Arg) in pseudo code.

Arg seems to be a value rather than a type.
Is range effectively a parameterized type?

Perhaps this is wrong, if so please show me what is
really happening.  If my guess is accurate please show
me how static/dynamic checking would be done in the
first (Ada) case.  What I want is a description or
examples of those cases which would raise an error.

You also point out that

"There is nothing equivelant in C++ to declaring a new
type integer with restricted range"

I understand your point, yet it isn't clear to me in the
original example, what specifically is an integer.