Do resumable exceptions make any sense?

Question

Following up my previous question I wonder if resumable exceptions make any sense. It looks like nobody uses them in Java. Don't they use resumable exceptions because of Java limitations or just because they don't really need them?

Suppose, I want to create a file in a directory, which should exist but does not. I would probably prefer use a resumable exception (i.e. throw an exception, catch it and create the directory, and resume the execution) instead of testing if the directory exists every time I create a file. Does it make sense in general ?

Answer 1

Not directly related to Scala, but when the C++ exception mechanism was being designed, there were big arguments about resumption. Eventually, they looked at a very large codebase (not of C++) where resumption could have been used, and found only one instance of it, which could easily be re-written not to use it. Also, C++ committee members who had used resumption were solidly of the opinion that it caused nothing but problems. So it was decided that C++ should not support exception resumption. Designers of most other languages seem to be of the same opinion.

Answer 2

I believe resumable exceptions are more useful in language platforms where it is feasible to catch an exception, use the debugger to isolate the problem, change the code to fix the problem, and update the running system with the new code before resuming the program. Think the Lisp Machine, and maybe Smalltalk. Modern systems have moved away from that level of interactivity; I've never used a system like that (except emacs, but I'm a shallow emacs user), so take my answer with a grain of salt.

Note that resumable continuations are similar to continuations, which have other uses in their own right.