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Issue: CONDITION-RESTARTS (Version 1)
Here's some questions/comments that need to be factored into the
next draft on this issue...
1. Moon has suggested that COPY-CONDITION is not necessary. Does anyone
disagree? I am willing to remove it, but doing so will make this
proposal less `compatible.' I don't care much one way or the other, but
I don't want to be accused of being `callous' toward people who do care.
If this committee will back me up on the removal of that function and
the resulting compatibility problems that could in principle (though
perhaps not in practice) come up, then I'll make the change. Opinions?
2. Moon has also asked that the syntax to SIGNAL-WITH-RESTARTS and
SIGNAL-WITH-RESTARTS signal-argument-list &rest restart-clauses
ERROR-WITH-RESTARTS signal-argument-list &rest restart-clauses
so that you would write
(SIGNAL-WITH-RESTARTS ('FOOD-COLOR-ERROR :FOOD 'LETTUCE :COLOR 'PINK)
(SIGNAL-WITH-RESTARTS (MAKE-CONDITION 'FOOD-COLOR-ERROR
:FOOD 'LETTUCE :COLOR 'PINK)
If you wanted to use MAKE-CONDITION, you would then write:
(SIGNAL-WITH-RESTARTS ((MAKE-CONDITION 'FOOD-COLOR-ERROR
:FOOD 'LETTUCE :COLOR 'PINK))
The advantage of what he proposes is that you could write
(SIGNAL-WITH-RESTARTS ("Bad ~S color" 'FOOD)
and a condition object would be created implicitly as with SIGNAL. A
possible disadvantage is that
(SIGNAL-WITH-RESTARTS (FOO BAR BAZ)
might look to someone like the FOO in (FOO BAR BAZ) named a function
rather than a variable. Does anyone else have an opinion on this?
3. Rees has suggested that the syntax for WITH-CONDITION-RESTARTS should be
WITH-CONDITION-RESTARTS condition-form restarts-form &BODY forms
WITH-CONDITION-RESTARTS (condition-form restarts-form) &BODY forms
which it is now. Does anyone else have an opinion?
4. Rees has asked for advice about how the condition/restart association
might be implemented -- is some kind of alist structure held by a
special variable what was intended, or ought the condition have a
restarts slot. He and I talked a little about this and eventually he
agreed that it's pretty obvious that the relation should be externally
represented. It's important that the association not be done by a slot
in the condition because if you carry around the condition object after
you're done signalling, you don't want it to contain useless and/or
misleading information about restarts that no longer exist. I'll probably
add some notes to this effect when I generate the next draft.
This doesn't really require comment, unless someone seriously disagrees.