how to define a global variable in a function file, such that all helper functions in this function file can use this variable?

For example, I have following use case. There are bunch of helper functions in func.m file, which will use some global variable const. How can I declare them once, such that all helper functions in this function file can use them?

% func.m file
const = 10;

function res = func()
a = helper1();
b = helper2();
res = a + b;
end

function res = helper1()
res = const^2;
end


function res = helper2()
res = const * 10;
end

Answer 1

[Cris LaPierre]

I'd be careful of using global variables. See this page about nested functions, particularly the section about sharing variables between parent and nested functions.

Using the information provided there, I might rewrite your functions as follows.

% calling script
const = 10;
resOut = func(const)

resOut = 200

% func.m file
function res = func(const)
a = helper1();
b = helper2();
res = a + b;

function res = helper1()
% nested inside func, so can access const
res = const^2;
end

function res = helper2()
% nested inside func, so can access const
res = const * 10;
end
end