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Re: No exceptions?

From: Marshall <marshall.spight_at_gmail.com>
Date: 30 Jun 2006 08:11:24 -0700
Message-ID: <1151680284.212755.26830@d56g2000cwd.googlegroups.com>


paul c wrote:
> Bob Badour wrote:
> ...
> > The way to avoid exceptions is to treat them as compile-time errors.
>
> I take it you really mean "ONE way to avoid exceptions ...". For one
> thing, I am interested in being able to express "x join y" in advance of
> defining a header for "x" (and I would like to evaluate it as well if
> that is logically possible!).

When you say "in advance of" do you mean earlier in the source file, or earlier in execution?

Earlier in the source file might be accomodatable; this would just be a foward reference, and could be handled by the language implementation making two (or more) passes over the source before moving forward, which is not uncommon.

If you mean, earlier in execution, then you could certainly permit it. You could allow partial evaluation; that is, you make the result be a thunk which has no value yet, but which will automatically convert in to a value once the header becomes defined.

I'm not clear what problem you're trying to solve, though. If it is elimination of exceptional conditions, that's not exactly possible. Consider: read two numbers from the input line and divide. The use enters "0, 0". Now, you can certainly define *some* semantics for this, but however you slice it, you have a partial function that was invoked with values outside of the domain it is defined on.

Marshall Received on Fri Jun 30 2006 - 10:11:24 CDT

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