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Re: [Scheme-reports] library syntax: "visiting" a library left undefined?

Sam Tobin-Hochstadt scripsit:

> This is not correct for R6RS (even though Aziz's dissertation suggests
> otherwise).  Explicit phasing in R6RS, combined with expansion time
> side-effects, means that modules with no exports can be imported at
> some phase N, this choice of phase (a) cannot be deduced from the
> program and (b) affects the semantics of the program under
> consideration.

It sounds like this code is not portable to arbitrary R6RS
implementations, specifically those which ignore phasing information in
the library specifications, as any R6RS implementation is free to do.
This is not in itself a Bad Thing, but but it seems to undermine its
value as evidence that R6RS code can be both compliant and depend on
explicit phasing.

> While this may seem like a strange case, it and related idioms turn
> out to be important in the implementation of Typed Racket, as
> described in our Scheme Workshop 2007 paper.

I look forward to reading this paper.

In my last lifetime,                            John Cowan
I believed in reincarnation;                    http://www.ccil.org/~cowan
in this lifetime,                               cowan@x
I don't.  --Thiagi

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