[r6rs-discuss] "Unspecified"

From: Sam TH <samth>
Date: Fri Sep 22 15:20:39 2006

On Fri, 2006-09-22 at 13:00 -0400, William D Clinger wrote:

> Seriously, there are about four distinct issues here.

It seems that there's really one important controversy, which seems to
have been unresolved among the editors, that ought to take precedence:

> The most important issue is whether it is truly
> necessary to specify the value returned by the
> procedures that, in the current draft, are required
> to return the unspecified value.

That is, should (if #f #f) return a particular value, or not. It seems
that the current name for the value returned by that expression is a
compromise between those who want the result to be genuinely
unspecified, and those who want a particular value.

Once this question is resolved, the other questions seem much easier,
and mostly just a question of naming. The value could be named void, or
unit, or nil, or empty, or no-information, with appropriate
constructors, predicates, external representations. And if it was not
named "the unspecified value", then the question of phrasing the report
would be much easier.

Similarly, if the value does not exist, as Will and Jonathan would seem
to prefer, then the other questions are moot.

Thus, I think the first question Will poses needs to be decided before
the others are considered.

sam th
Received on Fri Sep 22 2006 - 15:21:02 UTC