It would be interesting if a language allowed control flow to jump between catches and exceptions with named sort of exceptions.
E.g., imagine in this example that the code code throw an invalid index exception, some calling code could catch that, and supply a new index, and control flow would resume from the throw expression.
This would be a complete mess, but it would be interesting nonetheless :)
I realize you could probably build this in lisp, but this (by default) seems to be missing the part about jumping back to where the exception was raised, instead of resuming flow control from where the restart was defined, iiuc.
There is nothing to build, restarts act on the location where the condition was raised. In a conditions system unwinding is a restart, conditions don't unwind before running handlers.
The ability to update a value would make no sense otherwise.
I repeat, what you describe is literally how common-lisp works. Today. And how it has worked for 40 odd years. Also smalltalk.
You can do it easily in any language with functions and flow control. Restarts and coroutines are just if-errs and CPS-natured code in disguise. The difference is only syntactic, and there are ways to reduce the noise to manageable levels.
