Per Bothner wrote:
> How difficult would it be to extend the matcher to pattern matching?

That would involve the design of a pattern language,
which could be based on the pattern language used for
macros but with extensions for the unary predicates
that acts as guards for the match.  If a pattern
variable is allowed to appear twice, then some kind
of equality test would have to come out true as well
as the guard predicate.

SRFI-85 might provide or make it easier to define the
equality test for such a matcher, but I think there
are enough new issues with matching, especially
matching of regular trees, to justify a separate SRFI.

Will