Is there any way to call a MATLAB "subfunction" from the outside the file?

Question

Possible Duplicate:
Is it possible to define more than one function per file in MATLAB?

In order to define a (not anonymous) function in MATLAB, you need to create a file with the same name as the function; e.g., a function called myfunc can be defined in a file myfunc.m as per:

function rtn = myfunc(arg)
% do some stuff
end

Suppose in this same file myfunc.m, I have also a sub-function, as in

function rtn = myfunc(arg)
% do some stuff
end

function rtn = mysubfunc(arg)
% do some other stuff
end

AFAIK, there is no way to access mysubfunc from execution happening anywhere outside of the subfunc.m file. I have been and continue to be annoyed by this little idiosyncrasy in MATLAB (R2010b). Am I wrong -- is there any way to call mysubfunc from outside myfunc.m?

Update: New question: Is there any good way to do this? or should I really just suck it up and keep on making more files?

No, you have to suck it up. I use a semi-namespace approach to make this less messy and encourage me to reuse my own code (e.g. in the project 'heatflux' I'll start all function names with hf_). — Alex, May 12 '11 at 07:14
What's your goal here? Do you just want to reduce the clutter of having each function in a separate file? — Andrew Janke, May 12 '11 at 18:28
if you need to access subfunc outside of myfunc, then almost by definition, it shouldn't be a subfunction. Subfunctions should be reserved for common functionality that is only pertinent in the context of the enclosing function. — Marc, May 13 '11 at 19:31
The goal is to indeed to reduce clutter (both in number of files and cognitive units). I'm solving a problem numerically and have a collection of different possible iteration schemes that all take the same input and produce the same output. Previously, was running an *iterate* function and toggling which iteration scheme, but the classdef is a very clean solution. Wanted to run the sub-function outside the file for testing purposes while rapid prototyping of a new method. — pariser, May 13 '11 at 21:51

score 9 · Accepted Answer · answered May 12 '11 at 18:41

You could make them all static methods on a utility class. The functions will be globally referenceable by name, but you only need to manage one M-file.

classdef mystuff % in mystuff.m
    %MYSTUFF Utility functions for something or other...
    methods (Static = true)
        function rtn = myfunc(arg)
        disp('myfunc');
        end

        function rtn = mysubfunc(arg)
        disp('mysubfunc');
        end
    end
end

On the downside, you'll need to qualify or import all references to them, like mystuff.myfunc(). An "import mystuff.*" can take care of this for code outside of the class.

import mystuff.*
myfunc()
mysubfunc()

Within the class, calls between the functions will need to be qualified. (Big wart in Matlab's MCOS syntax, IMHO.) Also, they'll have more calling overhead than regular functions, so your code will be slower if you're calling them in tight loops. On the upside, now they're class members, and you can refactor them to make use of private class fields and functions and so on.

If you want to organize your codebase, you can stick them in a namespace by putting them in a directory whose name starts with a "+". Same number of files, but at least you have some structure to your dirs.

Thanks Andrew, this looks like a clean solution. – pariser May 13 '11 at 21:53 — pariser, May 13 '11 at 21:53

Mikhail Poda · Answer 2 · 2011-05-13T20:35:48.387

1

Accessing through function handles. It can be seen as OO emulation (static methods). I do not recommend you to use this technique though.

function obj = mainFunc()
obj.myFunc = @myFunc;
obj.mySubFunc = @mySubFunc;
end

function rtn = myFunc(arg)
% do some stuff
end

function rtn = mySubFunc(arg)
% do some other stuff
end

edited May 13 '11 at 20:35

answered May 12 '11 at 05:44

Mikhail Poda

5,742
3
39
52

1

"Object emulation" as you have shown is probably a bad idea; but in general, I think that returning a function handle to a subfunction is a reasonable enough thing to do in MATLAB. – Edric May 12 '11 at 07:34
If you're going to go to this trouble, just make a utility class, like Andrew says, above. – Marc May 13 '11 at 19:29

Is there any way to call a MATLAB "subfunction" from the outside the file?

2 Answers2