SETF and sequence updater's return values

[Carl W. Hoffman <CWH at MIT-MC>]

    Date: 24 August 1981 02:17-EDT
    From: Glenn S. Burke <GSB at MIT-ML>

    ... my personal feeling is that the returned value should
    be undefined.  My own versions of setf, even the one written for
    protosystem 3 years ago, have always had the macro SETV which was
    like SETF but did guarantee the returned value.

In addition to allowing SETF optimizations, I feel this approach makes
code easier to read by tagging places in which an assignment is also used
for value.