[m-dev.] Delayed goals and if-then-else goals

[Zoltan Somogyi]

On 07-Jan-2004, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> The right thing for an implementation to do at this point
> is to _flounder_; that is, to report a run-time error or exception.
> Well, it is possible that there might be better alternatives,
> but this is at least the best current practice.

Floundering when the condition of an if-then-else contains as-yet unproven
constraints on local variables preserves correctness, but my intuition is
that it isn't all that useful, because it leads to runtime aborts in too many
programs. I think "a better alternative" is required for delays to work
in practice. I have the outlines of a possible solution in mind, but it
has pretty high cost, both in development time and run time.

Zoltan.
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