I tend to think of George Carette's SIOD Scheme interpreter when I think of "Lisp style C":

    LISP difference(LISP x,LISP y)
    {if NFLONUMP(x) err("wta(1st) to difference",x);
     if NULLP(y)
       return(flocons(-FLONM(x)));
     else
       {if NFLONUMP(y) err("wta(2nd) to difference",y);
        return(flocons(FLONM(x) - FLONM(y)));}}

http://people.delphiforums.com/gjc/siod.html

Of course, that's a Scheme interpreter, so it might be at least a little expected.