Re: throw or return

I think I would like continue to redo the try. I'm not totally clear what "avoid rethrow" would mean...

I really like try <statement> [ onerror [(variable decl)] <statement> ] [ finally <statement> ]

but note that I'd like all three to be statement, not { ... }, so you can write

try foo() onerror werror("got error!!1!¡\n");

if you like.

/ Mirar

Previous text:

2003-10-01 23:53: Subject: Re: throw or return

---

It is indeed a very flexible structure. Combined with that only explicit continue statements would avoid rethrowing, I think it would work well.

As for keywords, I think "try" and "onerror" fit best. Some examples:

Catch only I/O errors and report them on stderr:

try { do_stuff(); } onerror (Error err) if (err->is_io_error) { werror ("I/O error on %O: %s\n", err->file, err->description); continue; // Avoid rethrow. }

Catch and handle application specific errors, and log but rethrow I/O errors:

try { do_stuff(); } onerror (Error err) if (err->is_my_app_error) { handle_my_app_error (err); continue; // Avoid rethrow. } else { my_app_log ("Interrupted by error: %s\n", err->description); }

Clean up a cache no matter what happens:

int id = session_id++;
try {
  session_cache[id] = SessionObj();
  do_stuff();
}
onerror () {
  m_delete (session_cache, id);
  // All errors are rethrown here.
}
m_delete (session_cache, id);

The last case, to always do some cleanup, is common and it shows code duplication. To avoid that I'd like a Java-style "finally" clause too:

int id = session_id++;
try {
  session_cache[id] = SessionObj();
  do_stuff();
}
onerror (Error err)
  if (err->is_my_app_error) {
    handle_my_app_error (err);
    continue; // Avoid rethrow.
  }
finally {
  // This is always executed no matter what happens above.
  m_delete (session_cache, id);
  // If the try block was interrupted by an error other than the
  // my_app type, it's rethrown here.
}

/ Martin Stjernholm, Roxen IS