It seems pointless at first, but I think it might be useful.  The
attached file (tested as an extension with 1.6.4) provides Scheme
bindings for defining smobs - i.e., the "print" and "equalp" functions
can be defined in Scheme.  This might be useful for adding
user-defined cases to equal?.  But I admit my real motivation for
writing this was to enable this gruesome hack:

guile> (define (printer smob-data port state) (system smob-data))
guile> (define generator (make-smob-type "smob-name" printer #f))
guile> (define ls (generator "ls"))
guile> (ls)
"ls"
guile> (ls "ls -a")
guile> (ls)
"ls -a"
guile> ls

... which shows me the output of "ls -a".  So I can use Guile as a
shell with a bit less typing.

Is there interest in adding this to libguile?  (Regardless, I think
the three snarfing macros at the top (along with corresponding
SCM_SMOB_FREE, SCM_SMOB_PRINT, and SCM_SMOB_EQUALP) would be useful
additions to smob.h, though perhaps the name SCM_ SMOB_APPLY is too
similar to the existing SCM_SMOB_APPLY_*.)


paul