%The program eliminates from the interval matrix [m,M] the rows containing
% (0,....,0) and the columns containing the transpose of (0,...,0)
  
function A=reduce(m,M)

  
  [p,q]=size(m);


% we construct the array v whose entries are the indices of the rows
% containing (0,....,0)
 
  v=zeros(1,0);
  for i=1:p
	  if sum(m(i,:).* M(i,:)<=0)==q
	  %that is every entry of the i-th row contains 0
	  v=[v,i];
end
	  end



% we construct the array w whose entries are the indices of the columns
% containing the transpose of (0,....,0)


w=zeros(1,0);
  for j=1:q
          if sum(m(:,j).* M(:,j)<=0)==p
          %that is every entry of the j-th column contains 0
	  w=[w,j];
end
	  end
	  
          m1=m(setdiff([1:p],v), setdiff([1:q],w))
	  M1=M(setdiff([1:p],v), setdiff([1:q],w))

          

  A=[m1,M1];