function tf = ispure(q)
% ISPURE   Tests whether a quaternion is pure.
% tf = ispure(q) returns 1 if q has no scalar part, 0 if not.
% Note that if q has a scalar part which is zero, ispure(q) returns 1.

% Copyright © 2005 Stephen J. Sangwine and Nicolas Le Bihan.
% See the file : Copyright.m for further details.

error(nargchk(1, 1, nargin)), error(nargoutchk(0, 1, nargout))

% Implementation note. This function uses ispure_internal, so that the knowledge of
% how quaternions are represented is hidden in the private functions.

tf = ispure_internal(q);