$ clisp

<...snip...>

[1]> (load "quarto.l")
;; Loading file quarto.l ...
;;  Loading file lp.l ...
;;  Loaded file lp.l
;; Loaded file quarto.l
T
[2]> (task81--place-piece-on-board-demo)
D    [B-] **** **** ****
C    **** [B+] **** ****
B    **** **** [b-] ****
A    **** **** **** [b+]
     1    2    3    4
On which cell will you place [B-], X?
(A1 A2 A3 B1 B2 B4 C1 C3 C4 D2 D3 D4)
> A1
X:  Placing piece [B-] on cell A1 ...
D    [B-] **** **** ****
C    **** [B+] **** ****
B    **** **** [b-] ****
A    [B-] **** **** [b+]
     1    2    3    4
On which cell will you place [B+], X?
(A2 A3 B1 B2 B4 C1 C3 C4 D2 D3 D4)
> B4
X:  Placing piece [B+] on cell B4 ...
D    [B-] **** **** ****
C    **** [B+] **** ****
B    **** **** [b-] [B+]
A    [B-] **** **** [b+]
     1    2    3    4
On which cell will you place (r-), X?
(A2 A3 B1 B2 C1 C3 C4 D2 D3 D4)
> C1
X:  Placing piece (r-) on cell C1 ...
D    [B-] **** **** ****
C    (r-) [B+] **** ****
B    **** **** [b-] [B+]
A    [B-] **** **** [b+]
     1    2    3    4
NIL
[3]> (bye)
Bye.