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Re: [Scheme-reports] Some comments after reading the r7rs public draft
On Mon, Jun 11, 2012 at 12:57 PM, John Cowan <cowan@x> wrote:
> Alex Shinn scripsit:
>> Chibi-scheme allows implicit forcing as a compile time option (probably
>> eventually to be a language-level option), and has a formal definition
>> of which primitives can and can't perform implicit forcing.
> Is this written down anywhere? I wasn't able to find it.
Not documented, per se, but basically _all_ primitives
except constructors (opcode class SEXP_OPC_CONSTRUCTOR)
auto-forced their arguments. I should probably change
that so that mutators (e.g. the second arg to vector-set!)
are not auto-forced.
(not (make-promise #f)) is an interesting case. It's
unspecified as far as the standard is concerned, and
I don't see any reason to deviate from the above rules
for it, so Chibi will continue to return #t here.
I think it's reasonable to say "it is an error if the
forced expression raises an exception."
The other cases I think should always be auto-forced -
they would simply be errors anyway.
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