OPERATION NOT HANDLED

[Ashwin Ram <ram-ashwin@YALE.ARPA>]

What's the best way of "trapping" a "operation not handled" error, in the
sense of being able to specify an action rather than break with the usual
error?  For example, consider a procedure (or operation) that would behave
like WHERE-DEFINED, except it would return NIL (rather than breaking) if the
object didn't handle the WHERE-DEFINED operation (e.g., tables and
read-tables don't).  Is there any way to find out if a given object handles a
given operation before calling it, or any way to trap the resulting error if
it does get called?

-- Ashwin.

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