~ Tower of Hanoi
( "!How many disks? " ? d: d. 0 > ^
   #H,d., "left","right","middle"; )
$H 1% d:
   d. 1 = [ #M,2%,3%; @ ]
   d. 1-d:
   #H,d.,2%,4%,3%;
   #M,2%,3%;
   #H,d.,4%,3%,2%; @
$M "Move " 1% " to " 2% "!" @