[R6RS] safe and unsafe; declarations

[Michael Sperber]

William D Clinger <will at ccs.neu.edu> writes:

> Mike wrote:
>> I'm not sure I understand this now---the main reason, I think is this
>> talk of exception handlers.  Isn't the R6RS mostly going to specify
>> what exceptions are *raised*, and leave the handling to the
>> application?
>
> My concept is that the R6RS will specify which exceptions
> are raised (whether required, encouraged, or allowed).
>
> The R6RS will also specify how exceptions are handled in
> safe mode.
>
> The R6RS will explicitly *not* specify how exceptions are
> handled in unsafe mode.  This allows implementations to
> handle exceptions in arbitrarily perverse ways when in
> unsafe mode.
>
> As I say, that is my concept.  The editors don't have to
> agree to it.

I'm not disagreeing (at this point, anyway).  I'm still trying to
understand.

Now, when you say that the R6RS specifies how exceptions are
"handled", you mean that the R6RS specifies what the default handler
is, right?  (I.e. that a program might catch the exception itself
using GUARD.)  When you say that unsafe mode affects how exceptions
are handled, does it now affect how exceptions are raised?
I.e. could a user program still catch them reliably?  (I think that's
not what you mean.)  Or are two different notions of "exceptions" at
work in the terminology?

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla