Re: Why no Propagates?

[gauthier@unilim.fr (Michel Gauthier)]

In article <54hjb7$bmm$1@goanna.cs.rmit.edu.au>, ok@goanna.cs.rmit.edu.au
(Richard A. O'Keefe) wrote:

>>  gauthier@unilim.fr (Michel Gauthier) writes:
>>  [about Java-like exception annotations]
>>  
>>  >I fully agree that " it would be a cool feature to have", but I concluded
>>  >long ago that it would be very difficult to make it compatible with
>>  >all the other features of the language. Possibly an additional effort
>>  >on ANNotated Ada in this direction would have been useful, but
>>  >we cannot hope a full solution.
>>  
>>  Just a suggestion:
>>      this is precisely the kind of thing which a compiler can find out
>>      for you and put in a cross-reference file or listing or hypertext
>>      or whatever.
>>  
>>  Typically, what you want to know is not "what exceptions can this procedure
>>  raise" but "where is this exception raised" or "what exceptions might reach
>>  this handler", which the Java syntax doesn't help with as much as one might
>>  hope.

Yes,  Richard, I agree.

Additionally, a thesis work is in process about such an issue.

But it is not as simple as we could wish. Without genericity
and exception identities, things goes rather well, but there is a
need of eliminating "unreachable raises" by program proofs.
How reliable are these proofs ?

If you add genericity, this requires additional parameterisation
by sets of exceptionbs (alone exceptions are not powerful enough).
Such parameters are not necessarily required by the language rules.
Of course, access-to-subprograms make the same problem arise.

If you add exception identities, then you can pray, or prefer good
style rules, or even insert sensible assertions. In this case, 
assertions are required with all exception raises, which very few
people do.

This is what I intended to say in my initial message.

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