Problem 45266. Restricted Subtraction v1

Created by Jonathan

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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!
See also:
Restricted Addition v1, Restricted Addition v2, Restricted Addition v3, Restricted Addition v4
Restricted Subtraction v1
Restricted Multiplication v1

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Last Solution submitted on Oct 17, 2025

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Rafael S.T. Vieira on 7 Nov 2020

Please, do not use isequal with floats, prefer abs(a-b) < tol. I've found a solution, but it gives an error of order 1e-15. Rounding solutions to 10 or 14 decimal places is close enough. And looking at all other solutions so far, I am the first one to truly solve this problem (please, try my commented code).

goc3 on 9 Nov 2020

Wow! That was hard to fix. The problem now tests against a tolerance of 1e–10. I also had to update a few of the anti-hacking checks to allow for a solution. Thanks to Rafael S.T. Vieira for providing a solution that could be used as a reference while fixing the test suite.

goc3 on 9 Nov 2020

I also deleted the most recent hacking solutions.

Rafael S.T. Vieira on 14 Nov 2020

Thanks again for fixing it, Grant. :)

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Problem 45266. Restricted Subtraction v1

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Problem 45266. Restricted Subtraction v1

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