[rules-users] looping due to immediate retraction

[John J. Franey]

OK. It took me a few laps with the debugger to understand what is happening
with the following:

rule
  when
     $assignment: Assignment($resource: resource)
     not Booking(resource == $resource)
  then
     insertLogical(new Booking($resource));
end


Basically, in the rhs the insertion of the new Booking causes the lhs to be
reevaluated, and since in the reevaluation, there IS a Booking, it is
retracted.  Then the lhs is reevaluated to see that there is NOT a Booking,
and so the rhs is run again, and loop and loop and loop.


But what I don't understand, is if I add an update in the rhs like this:


rule
  when
     $assignment: Assignment($resource: resource)
     not Booking(resource == $resource)
  then
    update($assignment);
    insertLogical(new Booking($resource));
end


there isn't a loop.  I didn't take the journey with the debugger to answer
this question, but am still wondering: why does the update  break the
infinite loop?

Thanks,
John

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