Question- Function for Signal Addition:

function [y,n] = sigadd(x1,n1,x2,n2)
% implements y[n] = x1[n] + x2[n]
% y = sum sequence over n, which includes n1 and n2
% x1 = first sequence over n1
% x2 = second sequence over n2 (n2 can be different from n1)
a = [1 2 3]
ax = -2:0
b = [4 5 6]
bx = 0:2
[z,v] = addition(a, ax, b ,bx)
function [add,n3] = addition(x, n1, y, n2)
n3 =min (min(n1) ,min( n2 ) ) : max ( max ( n1 ) , max ( n2 ) );
s1 =zeros(1,length (n3) );
s2 =s1;
s1 (find ( ( n3>=min( n1 ) ) & ( n3 <=max ( n1 ) )==1 ) )=x;
s2 (find ( ( n3>=min ( n2 ) ) & ( n3 <=max ( n2 ))==1) )=y;
add=s1 +s2;
end