Date: Fri, 29 Jun 2012 11:24:36 -0700 From: Alex Shinn <[email protected]>
> Richard Kelsey scripsit: > > Date: Thu, 28 Jun 2012 17:55:54 -0400 > From: John Cowan <[email protected]> > > The report should describe the semantics of dynamic variables, not one > particular implementation. The report describes the semantics in terms of dynamic extent, so the analogy to dynamic-wind seems appropriate. No, the description of dynamic bindings doesn't mention dynamic extent. The current text uses the phrases "during the evaluation of the body" and "evaluated in a dynamic environment in which ..." which in the presence of call/cc and dynamic-wind, and in the absence of a definition of dynamic environments, are far from clear. We do need to be careful here, and the WG has not yet had time to fully review the non-call/cc-based dynamic-binding research pointed out by Oleg. Can you give me a pointer to this? > Editorial tickets #427 and #428 created. Ballot ticket #429 for new > formal semantics created. If nobody steps up to do this and review it > before the last ballot, it will be closed. > > If the WG makes changes to the language that require changes to the > formal semantics, then they need to change the formal semantics. That > seems like part of the job. The formal semantics only covered a small subset of the language to begin with. The change in question is equivalent to adding a formal semantics for dynamic-wind, which was already missing from R5RS. I agree, of course, that we should fix this, or consider using (a subset of) the operational semantics from R6RS (which again is a subset of the language but at least has dynamic-wind). My comment was meant to be a more general response to John Cowan's planning to close a ticket if there was no one on the committee willing to work on the semantics. I was actually thinking of eqv?, where the report and the formal semantics no longer agree. In that case something does need to be done. For dynamic-wind and parameterize I agree that adding them to the semantics is desirable but isn't necessary. I do not agree that this would be equivalent to adding a formal semantics for dynamic-wind, for a couple of reasons. One is that dynamic bindings are used by the report itself, unlike dynamic-wind. The other is that having both dynamic-wind and parameterize in the language makes having a formal semantics for them more important than if only one or the other were present. -Richard Kelsey _______________________________________________ Scheme-reports mailing list [email protected] http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports
