Ceci n'est pas une value (was Re: [R6RS] "void" or "unspecific")

Anton van Straaten anton at appsolutions.com
Wed May 3 14:25:16 EDT 2006

William D Clinger wrote:
> By the way, here is some background information on precedent
> for issue 33:
> MzScheme, Chez Scheme, and Gambit use some variation of "void".
> Bigloo, SCM, Guile, Chicken, and Larceny use some variation of
> "unspecified".
> Scheme48 uses #{Unspecific}.

Related to this, the last two or three status reports have specified 
that R6RS will have "read-write invariance for every datum".  Our final 
vote on #3 today was to not add #!unspecified as syntax.  How, then, 
will read-write invariance work in a case such as:

   (write (list (unspecified)))



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