\" The Towers Of Hanoi
\" troff
\" Copyright (C) 1999 Amit Singh. All Rights Reserved.
\" http://hanoi.kernelthread.com
\"
\" Usage "troff -a hanoi.troff"

\" Define a sane upper limit on the maximum number of disks permissible
.nr M 10

.de usage
usage: \.Hanoi(N), where N is a positive integer (0 < N <= \nM)
..

\" doHanoi(N, from, using, to)
\" Recursive macro to solve Towers Of Hanoi
\"
.de doHanoi
.if \\$1 \{ \" (N > 0)
\" move (N - 1): 'from' to 'using' using 'to'
.doHanoi \\$1-1 \\$2 \\$4 \\$3
\\$2 --> \\$4
\" move (N - 1): 'using' to 'to' using 'from'
.doHanoi \\$1-1 \\$3 \\$2 \\$4
\}
.el \{ \" (N <= 0)
\\$2 --> \\$4
\}
..

\" Hanoi(N)
\" * Wrapper macro for calling doHanoi
\" * N is a positive integer (< \nM, for the sake of sanity)
\" 
.de Hanoi
.ie \\$1 \{ \" (N > 0)
.ie \\$1-\nM \{ \" (N > \nM)
.usage
\}
.el .doHanoi \\$1 1 2 3
\} \" (N <= 0)
.el .usage
..

\" Use the Hanoi macro
.Hanoi 3