Hide lines of code in MATLAB

Question

I want to know If it's possible and how, to hide some parts of a line or whole lines of code from a script in MATLAB. For example:

if a=b
   x=y+1; x=x^2;
end

And have the x=x^2 hidden, but still run the process. I mean:

if a=b
       x=y+1; 
end

if you use windows, CTRL+R for commenting, CTRL+T for uncommenting — Ander Biguri, Dec 01 '16 at 14:27
Are you talking about hiding it but still running it? If so, WHY? — Suever, Dec 01 '16 at 14:27
Do you want to hide `x=x^2` and still want `x=x^2` to execute? I hope that's not what you're asking! :D but if you still want that, you can make a function and call that instead of `x=x^2`. Other than that, you need two *equals to* signs in `if` . i.e `if a==b` — Sardar Usama, Dec 01 '16 at 14:31
Yes, ofc if a==b (that was a mistake and an example). I want to make exactly that, but I mean not to be seen. I want to make a joke to a friend of mine, but he could spot the difference because he knows how to code. The function would be visible, so that won't work. Thanks again! — Dimitris Boukosis, Dec 01 '16 at 14:37
http://i2.kym-cdn.com/photos/images/newsfeed/000/698/489/2f7.png — Sardar Usama, Dec 01 '16 at 14:42

score 6 · Answer 1 · edited May 23 '17 at 11:46

(wringing hands with evil grin on face)

If you really want to mess with people like this, you're going to want to go down the operator overloading route. Come with me on a journey where you will almost certainly shoot yourself in the foot while trying to play a joke on someone else!

(lightning crackles over the laughter of a madman)

I've discussed this in a few other questions before (here and here). Basically, you can change the default behavior of built-in operators for MATLAB data types. In this case, we'll change how the plus operator works for variables of class double (the default variable type). Make a folder called @double on your MATLAB path, then create a file called plus.m and put the following code inside it:

function C = plus(A, B)

  C = builtin('plus', A, B);

  if strcmp(inputname(1), 'y')
    C = C.^2;
  end

end

Now, try it for yourself...

>> y=1;   % Initialize y
>> x=y+1
x =
     4    % Wait a minute...
>> x=1+1
x =
     2    % OK
>> x=1+y
x =
     2    % OK
>> x=y+1
x =
     4    % What?!
>> x=y+2;
x = 
     9    % No!!
>> y=3;
>> x=y+1
x =
    16    % Oh noes! I've been hax0red!!11!1!

How it works:

The new plus function shadows the built-in one, so it gets called when performing addition on doubles. It first invokes the built-in plus to do the actual addition using the builtin function. This is necessary, because if you wrote C=A+B; here it would call the phony plus again and cause infinite recursion. Then, it uses the inputname function to check what the variable name of the first input to the function is. If it's 'y', we square the result before returning it.

Have fun!!!

...and remember to remove it when you're done. ;)

score 5 · Answer 2 · edited May 23 '17 at 12:32

if a==b
    x = y+1;
    for ind = 1
        x = x^2;
    end
end

Bit of a wacky way, but you can collapse loop/end blocks like for and while loops. Simply click the - sign in the editor:

So for two or less lines this doesn't help you, but if you want to hide e.g. 40 lines, it shortens it appreciably.

Another option is to simply chuck in a hundred or so spaces and make it obfuscated:

if a==b
    x = y+1;                                                                                                                                          x = x^2;
end

Thanks to excaza the most obfuscated way of all to write x=x^2;:

eval(cast((sscanf('240,122,240,188,100,118', '%d,')./2)', 'like', ''))

I think I found a slightly more obfuscated way. >:) – gnovice Dec 01 '16 at 20:15 — gnovice, Dec 01 '16 at 20:15

Hide lines of code in MATLAB

2 Answers2