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Newsgroups: comp.lang.ada
Date: Thu, 30 Jul 2015 13:10:49 -0700 (PDT)
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Subject: Re: Running a preprocessor from GPS?
From: EGarrulo <egarrulo@gmail.com>
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Xref: number.nntp.giganews.com comp.lang.ada:194550
Date: 2015-07-30T13:10:49-07:00
List-Id: <comp.lang.ada>

On Thursday, July 30, 2015 at 9:32:17 PM UTC+2, Randy Brukardt wrote:
> "EGarrulo" wrote in message 
> > But is this a valid excuse? Aren't programming languages supposed to
> > let programmers write useful programs?
> 
> Within the language philosophy. If writing *your* useful programs is too 
> hard, then you are probably using the wrong language (or you need some 
> re-education, which I think applies more to the current case ;-).
> 
> ...
> > If Ada offered runtime typing by means of a type `Any`, then `Printf`
> > could be trivially written as:
> >
> >   type Printf_Arguments is array (Positive range <>) of Any;
> >
> >   procedure Printf (Format : String; Arguments : Printf_Arguments);
> 
> Surely, at the cost of all compile-time checking (because there isn't any).

But not all conversions can be checked during compilation, that is a fact
already.

> And there couldn't be any useful runtime checking, either

Why not?  Please explain me why this is acceptable:

   -- This conversion will fail if Some_Integer is bigger than what 
   -- Constrained_Integer_Type can hold.
   Some_Constrained_Integer := Constrained_Integer_Type (Some_Integer);

whilst this is not:

   -- This conversion will fail if Any doesn't contain an Integer.
   Some_Integer := Integer (Any);

I don't see any difference.  Both conversions can fail at runtime because types
don't match.

> unless Ada added Multiple Inheritance, which is unlikely), so such a 
> construct would be unsafe. (Exactly how unsafe depends on the capabilities 
> of the format string.)

If Printf took care of formatting, then the number of supported types would be
limited to standard types (incidentally, this is why I envisioned an alternative
where formatting happens before passing the arguments to Printf).