$ clisp

<...snip...>

[1]> (load "quarto.l")
;; Loading file quarto.l ...
;;  Loading file lp.l ...
;;  Loaded file lp.l
;; Loaded file quarto.l
T
[2]> (task65--four-in-a-diagonal-demo)
Quarto board with four in a diagonal...
D    (r-) (R+) (r-) (b-)
C    **** [R+] (B-) (B+)
B    [b+] [R-] [R+] [r-]
A    [B-] [B+] [b-] ****
     1    2    3    4
Four in a diagonal? T
Quarto board with nothing...
D    (r-) **** (r-) (b-)
C    **** [r+] (B-) (B+)
B    (b+) [R+] [R+] [r-]
A    [B-] [B+] [b-] ****
     1    2    3    4
Four in a diagonal? NIL
NIL
[3]> (bye)
Bye.