function [z,info] = msign(h,tol,maxit)
%
% MSIGN  computes the matrix sign of a symmetric matrix
%
% [z,info] = msign(h,tol,maxit) computes the matrix sign z
% of the symmetric matrix h by iteration.  The assumption
% that h is symmetric is not checked. Iteration is stopped
% at iteration n whenever n=maxit or
%     
%       norm{z(n) - z(n-1)}  <=  tol*norm{z(n)}
%
%   where norm is the matrix one norm.
%
%   Returned in z is the matrix sign of h unless the algorithm failed
%   to converge.  Returned in info(1) is the number of iterations
%   performed.  info(2)=1 if the algorithm halted because of an
%   attempted inversion of a singular matrix.
%
%
%   REFERENCES:
%         B.D.O. Anderson(1978)
%         Laub(1991)
%         E.W. Anderson, L.P. Hansen, E.R McGrattan and T.J Sargent(1996)
%   PROGRAM  WRITTEN BY:  E. W. Anderson    Nov 26, 1994



%  This file contains the documentation for the mex file MSIGN. This
%  file is not a MATLAB function.  If the following line of code
%  is executed then you have not properly installed the MEX files.

error('MEX file msign.* is not available');