/* $Id: towers.pl,v 321.1 2002-03-06 17:52:37-08 - - $ */

/*
* Towers problem.
*/

towers( N ) :-
	move( N, source, spare, target ).

move( 0, _, _, _ ) :-
	!.

move( N, Source, Spare, Target ) :-
	M is N - 1,
	move( M, Source, Target, Spare ),
	report( Source, Target ),
	move( M, Spare, Source, Target ).

report( Source, Target ) :-
	write( 'Move a disk from the ' ),
	write( Source ),
	write( ' peg to the ' ),
	write( Target ),
	write( ' peg.'),
	nl.