MATLAB Answers

Julian S

Define multible Global Variables

Asked by Julian S
on 19 May 2019 at 18:15
Latest activity Edited by Adam Danz
on 20 May 2019 at 11:36
i used to declare global variables like this.
global p
% Körper 1
p.b1 = 1;
p.h1 = 0.6;
p.h1s = 0.3;
p.hp = 0.5;
This isn´t working anymore. does somebody know why?


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1 Answer

Answer by Adam Danz
on 19 May 2019 at 18:38
Edited by Adam Danz
on 20 May 2019 at 11:36

Your declarations should (still) work. Don't forget that you must declare the global variables again in the local workspace in order to access them.
global p
p.b1 = 1;
p.h1 = 0.6;
function dontUseGlobalVariables()
global p
% Now you have access to the p structure.
Or maybe a clear() command cleared your global variable between it's declaration and its retreival.
But again, please see this link to this comment to learn why global variables are a sign of bad programming.


Good function name. :)
on 19 May 2019 at 21:53
The only additional advice I would give is this: if you absolutely need to use globals, use a long name that contains the name of your top level function and is very descriptive. Using a long avoids collisions with other functions that might be using a similarly named variable. You have 63 characters for your variable name, you should use more than just 1.
I you think the name is too long and cumbersome to work with, create a temporary copy internal to your function. If you are not modifying the global there is no downside, thanks to the copy-on-write behavior of Matlab.

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