message primitive

["Greg J. Badros" <gjb at cs dot washington dot edu>]

The error handling code has a printf-like formatting capability such
that %S and %s format subsequent arguments as write or display style
output, respectively.  This seems generally useful, but is not available 
at the scheme level, directly-- at least not that I can find [closest is 
`display-error':

SCM_DEFINE (scm_display_error, "display-error", 6, 0, 0,
           (SCM stack, SCM port, SCM subr, SCM message, SCM args, SCM rest),

but that has extra STACK PORT and SUBR arguments.  Would others like a
`message' primitive that would work like so:

(message "Foo: %S %s" (list "a" "b"))

outputs:

Foo: "a" b

?

Note that this primitive already exists as a C-only function,
scm_display_error_message, that we would just need to expose in the
API.  How do people feel about R[45]RS compatibility issues?  Is there
an easy way to require that a module be loaded before a primitive is
accessible?  We could call it `%message' and have some module re-export
the primitive under the nicer name `message', I suppose.

Thanks for feedback!

Greg