On Tue, 21 Dec 2010, John Cowan wrote:

> Peter Kourzanov scripsit:
>
>> Right. However, this still is an underspecified corner of Scheme. Even
>> in R6RS I don't see a mandate to always implement (case) via hygienic
>> macros (and have the system solve the rebinding). And neither do
>> implementors, in my experience.
>
> I have just added a WG1 ticket to require this in R7RS.

No, I think this would be wrong.  There is no requirement in R6RS to implement
CASE using macros at all, never mind hygienic macros.  The sematics of CASE is
perfectly well described in R6RS as part of the core, and precludes Peter's
interpretation already.

The existing description in terms of semantics is fine, and allows an
implementation to treat CASE as a core form, for example.  The standard should
remain agnostic as to how CASE is implemented.

Andre

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