\util.g

/*
 * simple program to solve the "Towers of Hanoi" problem.
 */

bool Print;
int N;

proc hanoi(*char fromPeg, usingPeg, toPeg; int n)void:
    int i;

    if n ~= 0 then
	hanoi(fromPeg, toPeg, usingPeg, n - 1);
	if Print then
	    for i from 1 upto N - n do
		write(' ');
	    od;
	    writeln("Move disk ", n, " from ", fromPeg,
		    " peg to ", toPeg, " peg.");
	fi;
	hanoi(usingPeg, fromPeg, toPeg, n - 1);
    fi;
corp;

proc main()void:
    channel input text chin;
    char ch;

    open(chin, GetPar());
    if read(chin; ch) and (ch = '-' or ch = '+') and
	    read(chin; N) and N >= 0 then
	Print := ch = '-';
	hanoi("left", "middle", "right", N);
    else
	writeln("Use is: hanoi {-|+}n     where n is \# of disks (>= 0)");
    fi;
corp;