raising exceptions Matthias Felleisen 11 Oct 1999 23:27 UTC

Does the following sentence

  A Scheme implementation ("the system") raises an exception whenever an
  error is to be signaled or whenever the system determines that evaluation
  cannot proceed in a manner consistent with the semantics of Scheme.

mean that a Scheme system must raise an exception whenever the R5RS says
"unspecified" or is it merely allowed to raise an exception in such cases?

-- Matthias