How can I access subfunctions from outside the main function in MATLAB?

I have a function file that contains some subfunctions, as in the example below:

function foo1

       disp('This function contains subfunctions it can call.')

       foo2;

       foo3;

function foo2

       disp('in foo2');

function foo3

       disp('in foo3');

I would like to access subfunctions "foo2" and "f003" from outside the function (similar to the "include" functionality in C).

Answer 1

[MathWorks Support Team]

The ability to access subfunctions from outside of a function file via an "include" functionality is not available in MATLAB.

To work around this issue, a main function can provide a structure of subfunction function handles as an output argument. As an example, modify the function "foo1" as follows and save it in a file named foo1.m:

function fun_api = foo1

       fun_api.foo2 = @foo2;

       fun_api.foo3 = @foo3;

function foo2

       disp('in foo2');

function foo3

       disp('in foo3');

Subfunctions foo2 and foo3 can now be called from outside of foo1.m in the following manner:

fun_api = foo1;

fun_api.foo2();

fun_api.foo3();

Answer 2

[Xiangrui Li]

Here are two methods I use to access local functions. The m file may look like this:

function varargout = myMainFunc(in, varargin)
% myMainFunc can do its own job as designed, and it typically calls those local
% functions within the m file. 

% We mis-use the first two input, if any, to access all local functions
% You will need to insert this if-block into the beginning of your main function
if nargin>1 && (ischar(in) || isStringScalar(in))
    if in == "LocalFunc" % call local function with optional input/output
        [varargout{1:nargout}] = feval(varargin{:});
        return; % we are accessing local function only, so skip rest in the main function
    elseif in == "FuncHandle" % return a handle to use from outside the main function
        varargout{1} = str2func(varargin{1});
        return;
    end
end

% Here may be the lengthy main code which calls local functions somewhere
out = mySubFunc(in); % the input can be any data type as designed
% ...

function out = mySubFunc(in1)
% This is the local function doing its own job
disp("Input to mySubFunc is " + in1);
out = in1 * 2;

Outside the m file, we can call mySubFunc directly:

myMainFunc('LocalFunc', 'mySubFunc', 123)

This gives

Input to mySubFunc is 123

If mySubFunc may be used multiple times, we can get its function handle to avoid above long syntax:

mySubFunc = myMainFunc('FuncHandle', 'mySubFunc'); % return the handle
mySubFunc(123) % use it like regular function
out = mySubFunc(3)

The varialbe input/output in the if-block will take care of possibly variable input/output of different local functions, so make the syntax more general. The only sacrifice is that the keywords LocalFunc and FuncHandle can not be used as general input to the main function.