function s=subsets(k,n)

% SUBSETS S = SUBSETS(k,n) lists all subsets of k elements
%	out of a set of n elements.
%       n and k must be positive integers.
%
%	See also MINORS.

%	Adapted from Harold M. Edwards, "Linear Algebra."
%	Written by Serge Tchikanda 02/09/96.

if any([k n]) <= 0
   break
end

if n==k
   s=1:n;
elseif k==1
   s=[1:n]';
else
   c=prod(n-k+1:n-1)/prod(1:k-1);  % k-1  choose n-1
   s1=subsets(k,n-1);
   s2=subsets(k-1,n-1);
   s3=n*ones(c,1);
   s=[s1;[s2 s3]];
end