SETF of pathname components

[Glenn S. Burke <GSB@MIT-MC.ARPA>]

    Date: Tue, 15 Oct 85 15:25 EDT
    From: Robert W. Kerns <RWK@SCRC-YUKON.ARPA>

    . . .

    For uniformity we could extend this to other read-only accessors
    like SYMBOL-NAME, and DENOMINATOR although it's hard to see it as
    useful in the former case, and it's pretty strange in the later
    (and probably indicative of a woefully ineffecient program).

I agree with Moon's analysis, but i disagree that on these grounds
SETF should handle pathname components like LDB handles integers.  I
don't think pathnames appear to be sufficiently non-structured that
the read-only-ness of the components should be taken advantage of
in order to permit this hack.

The same goes for symbol-name.  As for denominator, it sounds
sufficiently ludicrous that i think it also should be left out, but
only because it seems perverse.