Re: Ada

[Robert Dewar <robert_dewar@my-deja.com>]

In article <t7aemmtz3b.fsf@calumny.jyacc.com>,
  Hyman Rosen <hymie@prolifics.com> wrote:

> C++ provides excellent implementation of generics,

The trouble with templates is that there is no equivalent of
the generic contract model, and also it is very difficult to
implement generic sharing of code. These are both issues
which the Ada model regards as essential, so certainly
by Ada standards, the above statement is controversial.


> and good implementation of overloading

OUCH! The rules for overloading in C++ are fiersomely complex,
far more so than in Ada, due to the interaction with implicit
conversions (something that Ada avoids), and the consequent
need for complex preference rules. In my experience, almost
no C++ programmers can tell you what the rules are, and many
people run into trouble with these rules.

> except that
> one cannot overload on return type as in Ada.

A pretty big gap! It means for example that if you have
multiple implementations of sets, that you cannot have
a parameterless function Empty that returns the (appropriate)
empty set.

> Is there something specific you believe you can not
> do in C++ with regard to these abilities?

Yes, see the above, in particular, to summarize:

1. Share generic code at the object level
2. Be sure your template is correct *before* you use it
3. Understand the overloading rules
4. Overload on return type


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