$ clisp

<...snip...>

[1]> (load "quarto.l")
;; Loading file quarto.l ...
;;  Loading file lp.l ...
;;  Loaded file lp.l
;; Loaded file quarto.l
T
[2]> (task70--change-player-demo)
Name of player 1? foo
Name of player 2? bar
Who will move first, FOO or BAR? foo
< PLAYER NAME =FOO >
< PLAYER NAME =BAR >
Change player...
< PLAYER NAME =BAR >
< PLAYER NAME =FOO >
Change player...
< PLAYER NAME =FOO >
< PLAYER NAME =BAR >
NIL
[3]> (bye)
Bye.