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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Exception types?
Date: 1998/06/08
Message-ID: <m3hg1vd4lw.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 360895065
References: <Pine.BSF.3.96.980608083034.15065A-100000@shell5.ba.best.com>
Organization: Network Intensive
Newsgroups: comp.lang.ada
Date: 1998-06-08T00:00:00+00:00
List-Id: <comp.lang.ada>


Brian Rogoff <bpr@shell5.ba.best.com> writes:

> One of the things that always bothered me about exceptions in Ada 
> is that they are not really integrated into the type system, for example, 
> they are not part of a generic signature package. I looked through the 
> Ada 95 and Ada 83 Rationales to try to find a discussion of this topic, 
> but I couldn't find one. Is there some record available? 

Mats Weber pointed this out too, in his PhD thesis.

You can work around this feature by importing a package that contains an
exception declaration.  This is how Text_IO works, by importing package
IO_Exceptions.

Sort of like:

package Compiler_Exceptions is

   Syntax_Error : exception;

end;

generic
   procedure Scan (...);  
   --
   -- Raises Compiler_Exceptions.Syntax_Error.
...
package GP is ...;

An then the actual subprogram can import the Compiler_Exceptions package
too.

Actually, in Ada 95 this can be integrated with the package hierarchy.
This is how Ada.Strings... works.  All the exceptions are declared in
the root package.