On Fri, 29 Apr 2011, Andre van Tonder wrote:

> On Fri, 29 Apr 2011, John Cowan wrote:
>
>>> WG2 will have explicit renaming only.
>>
>> If you're curious: explicit renaming was voted up 4-0; syntactic
>> closures voted down 1-3; and syntax-case tied with 3-3 (with one vote
>> for sending it to a future WG), which means it failed.  There were 11 WG
>> members at the time, of which 2 did not vote at all.
>
> I hope the committee took into account that for systems like Racket and Chez
> that are based on a native psyntax-type macro implementation, providing ER
> macros would adversely affect the complexity class of such macros, because in
> these systems an extra code walk is necessary to fully unwrap each input to the
> ER transformer.

Also, they cannot just use the original ER system, becasue it is not compatible
with modules or with syntax-case.  They would have to adopt a modified version
of ER such as the one provided in R6RS Larceny.  This adaptation has a couple of
additional primitives.  They are

     bound-identifier=? (procedure) - to compare bindings that are syntax
                                      objects, where original ER would use eqv?
     datum->syntax      (procedure) - for hygiene breaking where original ER
                                      would have inserted raw symbols into
                                      the output, incompatible with modules
                                      and with syntax-case

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