I have a with-handlers expression which handles several exceptions
appropriately and raises user-error exceptions, I have some additional code
I'd like to be executed after the exception have been handled, analogous to
dyanmic-wind's post-thunk argument or like the finally clause of a
conventional try{}catch{}finally{} structure found in other languages.
Documentation has shown that with-handlers and its cousins don't seem to
have anything like that so I thought I'd wrap my with-handlers expression
in a call-with-exception-handler to intercept the raised user-error
exceptions, do additional processing and returns the exception to continue
its propagation. It's not working and the installed exception handler
doesn't seem to be called at all.
Here's simplified code.
(call-with-exception-handler
(lambda (e)
...do more work
e)
(with-handlers ([exn:a? (lambda (e) (raise-user-error "exception exn:a
caught"))]
[exn:b? (lambda (e) (raise-user-error "exception
exn:b caught"))])
...code that may throw either exn:a or exn:b ))
My expectation was that the lambda installed by the
call-with-exception-handler would run after each user-error is raised. I do
see the user-error exceptions' messages being printed in the terminal so
they're being propagated all the way to the uncaught exception handler but
no work is being done by my own lambda handler. What am I doing wrong? More
to the point, is there a better way to do post with-handlers exception
handling processing?
My thinking is that I have a flawed understanding of the meaning of dynamic
extent of with-handlers and call-with-exception-handler forms.
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