This problem is Restricted Addition v4 with subtraction and more restrictions.
Subtract two inputs without use of common arithmetic operations. Unfortunately, in order to enforce this restriction, other restrictions are imposed. For example, use of 'e' is restricted to prevent use of 'eval' functions.
Until the Cody test system is changed, the hack below will work (as it currently does on every Cody problem). However, this type of solution is not appreciated.
function ans = fileread(~), ''
Other hacks are appreciated. If you can circumvent the restrictions (with your code running when called by tests 2, 3, ...) to use subtraction, then you have a valid and welcomed solution.
This version of the problem does not require hacks at all, just some basic MATLAB creativity!