Using a loop to make a function

This is the assignment that I was given:

The script should assume vec_in is specified at the command line. The
script should multiply the values at the odd locations of vec_in and
subtract the sum of values at the even location of vec_in. For example, given 

>> vec_in = [1 2 3 4 5]; script23;
vec_value =
  9    % This is the result of the calculation 1*3*5 – (2+4).

The phrases product and sum are not allowed to be used.

So far this is what I have come up with:

vec_in = [1 2 3 4 5]

for ii = vec_in(1:2:length(vec_in))
    vec_out_time = 
end
for jj = vec_in (2:2:length(vec_in))
    vec_out_add = 
end
vec_out = vec_out_time - vec_out_add

Any hints for how I can get around not using sum or product?

Answer 1

[Walter Roberson]

A = A + B
C = C * D

[Gina Barlage]

Thanks this helped a lot!