Re: unification

[stefan]

I did a reference implementation of unification code in pure 
scheme. It is just 185 lines of code (the rest is the test case)

see http://c-lambda.se/unify.scm

Some timings for the example
============================
scheme-version     > 2100 ms
c-initial-guile    > ~150 ms
current-best-guile >   73 ms 
sbcl               >   25 ms
gprolog            >  ~20 ms

So I've been able to tweak out 2x in guile + c

So what next?

This is what I will be playing with.
one need apart from a unification primitive also
be able to destruct a pattern into variable references
this can be done in a vm on a stack machine. And I will
now go on to let this vm be the guile vm itself. Later 
on when we the compiler starts to shine, I could hook into
that as well and generate target code. So this litle play will
spill over into being useful for the compiler later.
/Stefan