[m-rev.] diff: reset contains_trace_goal if necessary

[Ian MacLarty]

On Thu, Nov 09, 2006 at 03:02:07PM +1100, Mark Brown wrote:
> On 06-Nov-2006, Zoltan Somogyi <zs at csse.unimelb.edu.au> wrote:
> > @@ -2657,6 +2670,84 @@
> >  
> >  %-----------------------------------------------------------------------------%
> >  
> > +:- pred goal_contains_trace(hlds_goal::in, hlds_goal::out,
> > +    contains_trace_goal::out) is det.
> > +
> > +goal_contains_trace(GoalExpr0 - GoalInfo0, GoalExpr - GoalInfo,
> > +        ContainsTrace) :-
> > +    (
> 
> 	...
> 
> > +    ;
> > +        GoalExpr0 = scope(Reason, SubGoal0),
> > +        goal_contains_trace(SubGoal0, SubGoal, ContainsTrace),
> > +        GoalExpr = scope(Reason, SubGoal)
> 
> It appears that this goal feature propagates outside promise_pure scopes.
> I realise this behaviour follows what is in the reference manual, but is
> this really what we want?
> 
> I think that a goal which is explicitly promised pure should be able to
> be optimised away even if it contains trace goals, in the same way that
> a pure call can be optimised away even if there are trace goals in its
> definition.
> 
> Any comments?
> 

I agree, but I don't see what the difference between this and what I said
earlier is.

Ian.
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