Re: Why no exception hierarchy ?

[gauthier@unilim.fr (Michel Gauthier)]

In article <3ksv4s$f9e@news.uni-c.dk>, mojemj@unidhp.uni-c.dk (Mogens
Jensen) wrote:

>>  [...]
>>  
>>  As OOP has been built into the language, class hierarchies/libraries will 
>>  be built (or transferred from C++, maybe?); and these will probably throw 
>>  exceptions.
>>    As far as I can see, a hierarchy of exceptions would help a lot in such 
>>  a library.
>>  
>>  What is the rationale for this (I couldn't find it in either the AARM or 
>>  the Rationale).

I cannot answer about the rationale for this, but I can emphasize that
something like an exception hierarchy was already implementable in Ada-83, 
indeed with a lot of genericity (and crashes of the ...X... compiler).

Using Ada-95, exception identities are very similar to an 'exception type'.
You can pass them as parameters, store them in data structures if
suitable (stacks, queues, arrays, record fields). These stored exceptions
or parameter exceptions can be raised and handled (using the equality
operator).

The use of access discriminants to exception identities permits to
use an exception as a per-object parameter.

All these features are probably sufficient (I have not yet built this exception
hierarchy ) to satisfy your needs.

So, in fact, is there any real need for more specific features ?

-- 
Michel Gauthier - Laboratoire d'informatique - 123 avenue Albert Thomas
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