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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
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Subject: Re: Ada Popularity: Comparison of Ada/Charles with C++ STL (and Perl)
Date: Sat, 2 Oct 2004 18:33:41 -0500
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Date: 2004-10-02T18:33:41-05:00
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"K" <slatyb@yahoo.com> wrote in message
news:4c2ec8a8.0410012335.dcf9001@posting.google.com...
...
> than to maintain code like this:
>
>    read_order(DatabaseReader& reader, Order& order)
>    {
>      order.number = reader["ORDER.NUMBER"];
>      order.customer_number = reader["ORDER.CUSTOMER"];
>      order.acceptance_date = parse<Date>(reader["ORDER.ACCEPTED"]);
>      ...
>    }

It's orthogonal to your original point, but Ada contains features to make it
impossible to forget to modify some section of code when components are
added. That mitigates any needed duplication to some extent.

procedure Read_Order (Reader : DatabaseReader_Type; Order : in out
Order_Type) is
begin
    Order := (Number => Reader("Order.Number"),
                   Customer_Number => Reader("Order.Customer"),
                   ...);
end Read_Order;

If a component is added to Order, the compiler will complain if this
aggregate is not updated.

I'd probably use an enumeration type to map the names of the fields in order
to bring completeness checking to that side of the equation as well.

But I admit that I still can't figure out what it is that this "pointer to
member" does that is different than taking an access of a component. The
only thing that Ada doesn't have here is an equivalent to "void", which is
of course about safety - all access types have to have a designated type.

                     Randy.