function diff = minus(con1,con2)% Subtract two linear constraint objects%% Syntax:%   "C = a - b"%%   "C = minus(a,b)%% Description:%   "minus(a,b)" returns "C" a cell array of linearcon objects whose%   union represents "a-b".%% Examples:%   Given two linear constraint objects, "a" representing a square in the%   x3 = 0 plane with corners at (x1,x2) pairs (2,1), (2,3), (4,3), and%   (4,1) and "b", another square in the same plane with corners at (2,1),%   (2,2), (3,1), and (3,2),%%%%     "C = a - b"%%%%   returns "C", a cell array with elements,%%%%     "C{1} ="%%     "[ 1.000000 0.000000 ]x <= 4.000000"%%     "[ 0.000000 1.000000 ]x <= 3.000000"%%     "[ 0.000000 -1.000000 ]x <= -1.000000"%%     "[ -1.000000 0.000000 ]x <= -3.000000"%%%%     "C{2} ="%%     "[ -1.000000 0.000000 ]x <= -2.000000"%%     "[ 0.000000 1.000000 ]x <= 3.000000"%%     "[ 1.000000 0.000000 ]x <= 3.000000"%%     "[ 0.000000 -1.000000 ]x <= -2.000000"%%%% Note:%   It is assumed that "a" and "b" have the same equality constraint (if%   any), i.e they lie in the same subspace.%% See Also:%   linearconglobal GLOBAL_APPROX_PARAM[CE1,dE1,CI1,dI1] = linearcon_data(con1);[CE2,dE2,CI2,dI2] = linearcon_data(con2);% Handle some trivial casesif isempty(con1)  diff = {};  returnendif isempty(con2)  diff = {con1};  returnend% Check for illegal constraintsif (length(dE1) > 1) | (length(dE2) > 1)  error(['LINEARCON/MINUS: More than one equality constraint found in' ...	' one of the objects.'])  returnendif (length(dE1) ~= length(dE2))  error(['LINEARCON/MINUS: Both objects must have the same number' ...	' of equality contstraints.'])  returnendif length(dE1) == 1  hp_tol = GLOBAL_APPROX_PARAM.poly_hyperplane_tol;  if rank([CE1 dE1; CE2 dE2],hp_tol) > 1    error(['LINEARCON/MINUS: Both (n-1) dimensional objects must have ' ...	  ' the same equality contstraint.'])    return  endend% For i = 1,...,N where N is the number of inequality hyperplanes in con2,% Add hyperplanes 1,..,.N-1 and the Nth hyperplane with the sign for the% normal and b reversed to con1 and recompute the new region with these% hyperplane constraints.diff = {};for k = 1:size(CI2,1)  CIk = [CI2(1:k-1,:)         -CI2(k,:)];  dIk = [dI2(1:k-1,:)         -dI2(k,:)];  conk = con1 & linearcon([],[],CIk,dIk);  if ~isempty(conk)    diff{length(diff)+1} = conk;  endendreturn