abcddim

% -*- texinfo -*-
% @deftypefn {Function File} {[@var{n}, @var{m}, @var{p}] =} abcddim (@var{a}, @var{b}, @var{c}, @var{d})
% Check for compatibility of the dimensions of the matrices defining
% the linear system
% @iftex
% @tex
% $[A, B, C, D]$ corresponding to
% $$
% \eqalign{
%  {dx\over dt} &= A x + B u\cr
%             y &= C x + D u}
% $$
% @end tex
% @end iftex
% @ifinfo
% [A, B, C, D] corresponding to
%
% @example
% dx/dt = a x + b u
% y = c x + d u
% @end example
%
% @end ifinfo
% or a similar discrete-time system.
%
% If the matrices are compatibly dimensioned, then @code{abcddim} returns
%
% @table @var
% @item n
% The number of system states.
%
% @item m
% The number of system inputs.
%
% @item p
% The number of system outputs.
% @end table
%
% Otherwise @code{abcddim} returns @var{n} = @var{m} = @var{p} = @minus{}1.
%
% Note: n = 0 (pure gain block) is returned without warning.
% @seealso{is_abcd}
% @end deftypefn