subroutine igrad1( adj, add, xx,n, yy ) integer i, adj, add, n real xx(n), yy(n) call adjnull( adj, add, xx,n, yy,n ) do i= 1, n-1 { if( adj == 0 ) yy(i) = yy(i) + xx(i+1) - xx(i) else { xx(i+1) = xx(i+1) + yy(i) xx(i ) = xx(i ) - yy(i) } } return; end