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how to make a constant global so all packages files use it?

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hello! I would like to define a constant in such a way all my functions in the package folders use it , how can I do it ?? Thank you in advance .

Accepted Answer

Jan
Jan on 23 May 2017
As Stephen has explained already, passing variables as arguments is the best practice.
If you have really good reasons to define a constant globally, do not use global, but prefer a dedicated function, which provides the values as struct:
function C = myPackageConstants()
C.g = 9.81;
C.pi = 3.14159265;
C.VolumeOfHeidelbergBarrel = 221716; % liter
Then call this from all function as:
C = myPackageConstants;
This is less clear than using arguments. If it is called very often, it might matter that it has a certain runtime overhead. But in opposite to globals, you can be sure that the values are not modified anywhere, such that debugging gets horrible.
  2 Comments
Steven Lord
Steven Lord on 23 May 2017
Or if it's a single constant that is broadly usable, like pi, make it a function that returns just that one value. The pi function is built-in, but if it were written as a function file it would be just:
function P = pi
P = 3.14159265358979;

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More Answers (1)

Robert
Robert on 26 Feb 2021
You could also define a class with only constant properties. Contrary to Jan's solution, you can access the constants directly, without having to assign all of them to a variable first.
Calling it many times does not result in runtime overhead, like Jan said might be the case for his solution.
classdef Constants
properties (Constant)
g = 9.81
k = 1.234
end
end
Reference the constants using:
Constants.g
Of course, if the Constants class is in one of your packages, you have to include its namespace in the call.
  2 Comments
Florian B
Florian B on 5 Aug 2021
Edited: Florian B on 5 Aug 2021
Would using the reference as
x = Constants.g;
instantiate the object "Constants" though? Or is this a static property?
Rik
Rik on 5 Aug 2021
It is a static property for most intents and purposes.
You could easily see if multiple calls of this type will call the constructor multiple times by putting a disp in the constructor.

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