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 .
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.