bear wrote:
> It's different because #f is a useful value, not a signal that some
> operation failed or was invalid.

#f is often used to signal failure. For examples, look no further than
string->number and assoc.

> In general, operations that are
> supposed to retrieve a value can fail, and then what value do they
> return?

Yup, you've identified one of the oldest problems in interface design.

Alan
--
Dr Alan Watson
Centro de Radioastronomía y Astrofísica
Universidad Astronómico Nacional de México