On 08/29/2011 03:47 PM, Alex Shinn wrote:
> On Tue, Aug 30, 2011 at 3:26 AM, John Cowan<cowan@mercury.ccil.org>  wrote:
>>
>> "It is an error" does not mean "an error is signalled".  It's perfectly
>> fine for existing or future Schemes to store or output an undefined
>> value; it just isn't portable to do so.  So it is not invasive and breaks
>> nothing except user code like
>>
>>         (define x (set! y 32))
>>
>> which has no portable meaning in any case (it will not work in Racket, e.g.).
>
> Not true, as Eli pointed out.
>
> I'm unable to find a single implementation
> which does _not_ return a single unspecified
> value in these cases, despite the change in
> R6RS.

Kawa defines set! etc to return #!void which is defined
to be same as (values).

Kawa doesn't complain about (define x (set! y 32))
but it probably should.
--
	--Per Bothner
per@bothner.com   http://per.bothner.com/

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