[m-dev.] Adding default clauses to the language.

[Holger Krug]

On Thu, Aug 09, 2001 at 09:48:11PM +1000, Peter Schachte wrote:
> On Thu, Aug 09, 2001 at 09:15:09PM +1000, Fergus Henderson wrote:
> > :- func detmap3(func(T1, T2, T3) = T, list(T1), list(T2), list(T3)) = list(T).
> > :- never_fails detmap3(in, in, in) = out.

> I think it's probably going to be necessary in practice to explicitly
> specify the exception to throw instead of failing.
> 
> Quibble:  I don't think "never_fails" is a good name for it.  It sounds like
> it says this predicate called in this mode can't fail.  But the mode
> declaration already says that (or is this in place of the mode
> declaration?).  Anyway, what it really says is "in this mode, modify my code
> so that if it would fail, instead raise an exception."  Maybe "never_fail"
> or "ensure_no_failure" or "error_on_failure" would be better a name?

Maybe: 

:- failing detmap3(in, in, in) = out throws Exc.

or:

:- mode detmap3(in, in, in) = out is det ; throws Exc.

`Exc' could even be an expression, but then one would have to handle the
case if `Exc' throws an exception.

-- 
Holger Krug
hkrug at rationalizer.com
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