How does one tell if something is a function?

>>>>> "Barton" == Barton Willis  writes:

    Barton> -----maxima-admin@math.utexas.edu wrote: -----

    >> Nevermind, found mfboundp.

    Barton> There's a problem using mfboundp.

    Barton> (%i1) f(x) := x$
    Barton> (%i2) to_lisp()$
    Barton> Type (to-maxima) to restart
    MAXIMA> (mfboundp '$f)
    Barton> NIL
    MAXIMA> (mfboundp '|$f|)
    Barton> (MEXPR ((LAMBDA) ((MLIST) |$x|) |$x|))

    Barton> How does one convert $f to |$f|?

Somehow this doesn't seem right.  With maxima's case sensitivity and
case conversion, shouldn't $f (= $F) in lisp correspond to the
lowercase f function in maxima?  

Perhaps we forgot something when making maxima case-sensitive and
case-inverting?  The fact that (mfboundp '|$f|) produces an output
with |$x| instead of $X seems to indicate that.

Ray