macros

[Hal Abelson <hal@murren.ai.mit.edu>]

I am very unhappy that Will's current that R4RS it will not say
anything about macros.  One of the major agreements at the Snowbird
meeting was the agreements to go ahead with macros.  The momentum of
that decision has been lost, and we need to regain it.

Now that there is a (conservative) Scheme standard beign developed by
the IEEE group, I think we can afford to be less conservative in the
R4RS document.  So I don't feel bad about including something that we
may want to change in a later R*RS.

I think that, at minumum, R4RS should have a section entitiled
something like "Provisional proposal for macros".  This gives us the
option to change the details later, but it serves as a committment
that Scheme DOES have macros, and presents our best current ideas on
the subject.

The macro committee should get its collective head together and write
such a proposal.  Here are two possible forms the proposal might take:

(1) You guys can agree on something.

(2) You can write TWO proposals.  One would be along the lines of
extend-syntax; the other based upon semantic closures.  The full
proposal should descibe both of these, together with a brief
introduction that explains what the issues are, gives reasons why we
are not yet ready to commit to either proposal (hopefully there are
reasons, other than political ones), and sets forth some problems that
we hope to solve in future R*RS documents.  I nominate Jonathan Rees
to write this overview.


The main thing I want to avoid is for R4RS to appear with no macro
proposal at all.

Will, please give the macro committee a deadline for how long you will
wait for this report.  I don't see why it should take more than a week
or two to come up with the two-proposal option, at least.

-- Hal