[no subject]

[GLS at MIT-MC (Guy L. Steele, Jr.)]

    I think that // of one argument should be that argument, not zero
    as it presently is. ...
Your argument is well-taken, and is similar to the approach taken
in APL with respect to the reduction operator.  MacLISP, however,
purposely uses the "unary" forms of the noncommutative arithmetic
operators so that (- n) can mean what it "obviously" means,
i.e. negation.  By analogy with this, (// n) denotes the reciprocal
of n.  For fixnums this trivially produces zero, but for consistency
with flonums we must do this.