MATLAB: How to flip a row vector without using flip(lr) function

Question

I want to write a function that it can flip a row vector without flip(lr) function.

if true
  % A=[1 2 -3 4]
    And output must be:
    B=[4 -3 2 1]
end

Answer 1

Reverse the indices:

A = [1 2 -3 4];
B = A(numel(A):-1:1)
B =
     4    -3     2     1