Question-Function for Folding:

function [y,n] = sigfold(x,n)
% implements y[n] = x[−n]
% y = folded sequence over n
% x = input sequence over n
n = -1:2
x = [2 5 6 8]
[z,v] = flipsig(x,n)
zz = conv(z,x)
function [y,ny] = flipsig(s1, ns)
y = fliplr(s1)
ny = fliplr(-ns)
end