[stack] Constant folding algorithm

Hi all,

Right now, I'm working on a module called inverse for Factor. The
basic goal is to provide an inverse (or, technically, a section) of a
quotation, for a generalized form of pattern matching. I've noticed
that this can work both more efficiently and more generally if I first
perform constant folding on the quotation, for example transforming [
1 2 + * ] into [ 3 * ], which can more easily be inverted. Right now,
I have a very simple constant folding algorithm which looks for a word
in a certain predefined set of words, preceded by two constants. This
fails, though, if I use something like [ 1 2 + 3 4 + / ]. I'm
wondering if anyone has any idea of how to make an algorithm which,
given a quotation and a list of safe-to-fold words with their arities,
will perform as much constant folding as is possible on a function.
The Factor compiler implements constant folding, but it operates on an
intermediate dataflow representation rather than quotations. This
looks like one area where it's a little easier to manipulate an
applicative programming language than a concatenative one, though I'm
sure there's a good solution this problem. The first thing that comes
to mind is to use a slightly modified metacircular interpreter, but
that would be very complicated to implement. Ideas?

Daniel Ehrenberg