mpower.m

Robot tool box - provides many functions that are useful in robotics including such things as kinem

%MPOWER Raise quaternion to integer power
%
% Compound the quaternion with itself.  Invoked by means of the caret
% operator.

% Copyright (C) 1999-2008, by Peter I. Corke
%
% This file is part of The Robotics Toolbox for Matlab (RTB).
% 
% RTB is free software: you can redistribute it and/or modify
% it under the terms of the GNU Lesser General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
% 
% RTB is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU Lesser General Public License for more details.
% 
% You should have received a copy of the GNU Leser General Public License
% along with RTB.  If not, see <http://www.gnu.org/licenses/>.

function qp = mpower(q, p)

	% check that exponent is an integer
	if (p - floor(p)) ~= 0,
		error('quaternion exponent must be integer');
	end

	qp = q;

	% multiply by itself so many times
	for i = 2:abs(p),
		qp = qp * q;
	end

	% if exponent was negative, invert it
	if p<0,
		qp = inv(qp);
	end