I have a question concerning indicating unusual conditions in gambit. This is more a stylistic question rather then a technical question, but its worth knowing what others are doing.

Say I have a piece of library code that accepts an optional timeout. There are any number of things that could occur if the timeout expires. For example, in SML/Ocaml I would probably just raise an exception. That's pretty standard in that language and it costs almost nothing in overhead. In Erlang I would probably return a tuple like {timeout, some_other_data}. What is usual way to do this in gambit? Is it common to simply raise an exception? Is it more acceptable to return a special value like Erlang or C? I am thinking that raising an exception is the correct thing to do, but I wouldn't mind having confirmation on that.