[m-dev.] Re: exceptions

[Ralph Becket]

> -----Original Message-----
> From: Fergus Henderson [mailto:fjh at cs.mu.OZ.AU]
> 
> Does Modula 2+ have parametric polymorphism or higher-order 
> procedures?
> The additional complexity of declaring exceptions is
> a bit higher in the presence of these features.

Good point.  Still, if we have an exception typeclass hierarchy with a
root then we can just declare that polymorphic predicates may raise
error/1 or whatever name is decided upon.

> I'm not totally opposed to the idea of declaring exceptions.
> Certainly for safety-critical software, it's probably worthwhile.
> But in many cases I think the disadvantages will outweigh the
> advantages.
> 
> I'd be happy for Mercury to have compiler-checked 
> declarations of which
> exceptions a predicate would throw, so long as they were (by default)
> optional.  But it's not at all high on my personal list of priorities.

You're probably right, given the problems thrown up by higher order code.
Shame.

Ralph
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