function [ v, more ] = simplex_lattice_point_next ( n, c, v, more )
%*****************************************************************************80
%
%% simplex_lattice_point_next() returns the next simplex lattice point.
%
% Discussion:
%
% The lattice simplex is defined by the vertices:
%
% (0,0,...,0), (C(N+1)/C(1),0,...,0), (0,C(N+1)/C(2),...,0) ...
% (0,0,...C(N+1)/C(N))
%
% The lattice simplex is bounded by the lines
%
% 0 <= V(1:N),
% V(1) / C(1) + V(2) / C(2) + ... + V(N) / C(N) <= C(N+1)
%
% Lattice points are listed one at a time, starting at the origin,
% with V(1) increasing first.
%
% Licensing:
%
% This code is distributed under the GNU LGPL license.
%
% Modified:
%
% 08 July 2009
%
% Author:
%
% John Burkardt
%
% Input:
%
% integer N, the spatial dimension.
%
% integer C(N+1), coefficients defining the
% lattice simplex. These should be positive.
%
% integer V(N). On first call, the input
% value is not important. On a repeated call, the input value should
% be the output value from the previous call.
%
% logical MORE. On set MORE to FALSE to indicate
% that this is the first call for a given simplex. Thereafter, the input
% value should be the output value from the previous call.
%
% Output:
%
% integer V(N). V contains
% the next lattice point.
%
% logical MORE. MORE is TRUE if not only is the returned value V a lattice point,
% but the routine can be called again for another lattice point.
% If the output value is FALSE, then no more lattice points were found,
% and V was reset to 0, and the routine should not be called further
% for this simplex.
%
if ( ~more )
v(1:n) = 0;
more = 1;
else
c1n = i4vec_lcm ( n, c );
rhs = c1n * c(n+1);
lhs = 0;
for i = 1 : n
term = 1;
for j = 1 : n
if ( i == j )
term = term * v(j);
else
term = term * c(j);
end
end
lhs = lhs + term;
end
for i = 1 : n
if ( lhs + c1n / c(i) <= rhs )
v(i) = v(i) + 1;
more = 1;
return
end
lhs = lhs - c1n * v(i) / c(i);
v(i) = 0;
end
more = 0;
end
return
end