[plt-scheme] syntax and promises and possibly phases

OK, thank you, using a keyed table to store cached values would work in
this case.

I now have to admit that I was trying to use a concrete example to ask a
more general question about syntax extensions that cache values.

So I'm also curious if there's a way to solve this problem using a
hygienic macro, without using a table.  Intuition says there should be
an easy way.

(I asked on plt-scheme list before comp.lang.scheme, since the answer
might be sensitive to the trickiness of evaluation phases, and MzScheme
seems to know phase separation well.)

-- 
                                             http://www.neilvandyke.org/