// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA -
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution.  The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt

function st=statgain(sl)

    select typeof(sl)
    case "rational" then
        dom=sl("dt")
        if dom=="c" then
            st=freq(sl("num"),sl("den"),0)
        else
            st=freq(sl("num"),sl("den"),1)
        end;
    case "state-space" then
        dom=sl.dt;
        [m,p]=size(sl(2));
        if dom=="c" then
            if rank(sl(2)) <> m then
                error(msprintf(gettext("%s: Wrong values for input argument #%d: State matrix is singular.\n"),"statgain",1)),
            end
            st=sl(5)-sl(4)*inv(sl(2))*sl(3);
        else
            if rank(eye(m,m)-sl(2))<>m then
                error(msprintf(gettext("%s: Wrong values for input argument #%d: State matrix - eye is singular.\n"),"statgain",1))
            end
            st=sl(5)+sl(4)*inv(eye(m,m)-sl(2))*sl(3);
        end;
    else
        error(97,1)
    end

endfunction