macro expand in a specified module

[Keisuke Nishida]

I'd like to expand a macro in a specified module.
The following procedure does it:

  (define (expand e m)
    (cond
     ((pair? e) (let* ((a (car e))
                       (val (and (symbol? a) (module-ref m a))))
                  (if (defmacro? val)
                      (expand (apply (defmacro-transformer val) (cdr e)) m)
                      e)))
     (#t e)))

  guile> (define-module (foo))
  $1 = #<directory (foo) 80841c0>
  guile> (define-macro (foo x) `(* x x))
  guile> (define-module (bar))
  $2 = #<directory (bar) 8084170>
  guile> (macroexpand '(foo 2))
  $3 = (foo 2)
  guile> (expand '(foo 2) $1)
  $4 = (* x x)

May I add this to ice-9.scm?  I think this procedure looks good
because it is symmetry to eval.

Kei