% -*- texinfo -*-
% @deftypefn {Function File} {[@var{retval}, @var{pc}, @var{pf}] =} hinfsyn_chk (@var{a}, @var{b1}, @var{b2}, @var{c1}, @var{c2}, @var{d12}, @var{d21}, @var{g}, @var{ptol})
% Called by @code{hinfsyn} to see if gain @var{g} satisfies conditions in
% Theorem 3 of
% Doyle, Glover, Khargonekar, Francis, @cite{State Space Solutions to Standard}
% @iftex
% @tex
% $ { \cal H }_2 $ @cite{and} $ { \cal H }_\infty $
% @end tex
% @end iftex
% @ifinfo
% @cite{H-2 and H-infinity}
% @end ifinfo
% @cite{Control Problems}, @acronym{IEEE} @acronym{TAC} August 1989.
%
% @strong{Warning:} do not attempt to use this at home; no argument
% checking performed.
%
% @strong{Inputs}
%
% As returned by @code{is_dgkf}, except for:
% @table @var
% @item g
% candidate gain level
% @item ptol
% as in @code{hinfsyn}
% @end table
%
% @strong{Outputs}
% @table @var
% @item retval
% 1 if g exceeds optimal Hinf closed loop gain, else 0
% @item pc
% solution of ``regulator''
% @iftex
% @tex
% $ { \cal H }_\infty $
% @end tex
% @end iftex
% @ifinfo
% H-infinity
% @end ifinfo
% @acronym{ARE}
% @item pf
% solution of ``filter''
% @iftex
% @tex
% $ { \cal H }_\infty $
% @end tex
% @end iftex
% @ifinfo
% H-infinity
% @end ifinfo
% @acronym{ARE}
% @end table
% Do not attempt to use this at home; no argument checking performed.
% @end deftypefn