[R6RS] The unspecified values, multiple-value semantics and all
Anton van Straaten
anton at appsolutions.com
Tue Nov 7 04:06:03 EST 2006
William D Clinger wrote:
> * Do you really want to try to explain all this over in
> the R6RS discussion group?
I think we should make a decision, and (at some point) announce it.
For me, the main obvious choices are (a) to rename the unspecified value
to something less amusing; or (b) revert to R5RS semantics.
The concerns about the ramifications of a switch to zero-return values
haven't changed for me, no matter which variation on those semantics are
used. Will has laid them out very clearly.
Regarding (a), Will observed that the proposed unspecified value "did
not actually increase portability in any meaningful way." To me, the
main reason to standardize this at all would have been to achieve a
minor cosmetic standardization: the ability to write down (e.g. in
email, a book, or lecture notes) the external representation of the
value of expressions such as (list (if #f #f)), without having to
mention the umpteen pointlessly different ways that different Schemes
Since we haven't gone that far anyway, and if there isn't agreement for
that, then I don't see much reason not to revert to R5RS semantics.
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