Given a named function, how can I call this function, and not the subfunction of the same name?

My function is passed the name of a function (as a string). It just so happens that my function contains a subfunction of that name. I want to make sure I call the external function, instead of the subfunction. How can I achieve this?

E.g. save the following in test.m:

 function test
 feval(evalin('base', 'str2func(''help'')'), 'help');
 end

 function varargout = help(varargin)
 error('Should not get here!');
 [varargout{1:nargout}] = deal([]);
 end

Then calling test gives:

 >> test
 Error using test>help (line 6)
 Should not get here!

 Error in test (line 2)
 feval(evalin('base', 'str2func(''help'')'), 'help');

[Oliver Woodford]

I would say what I'm seeing is unexpected behaviour. Also, putting

 evalin('base', 'which(''help'')')

as the first line in the help subfunction gives:

 C:\....\test.m (help)  % Subfunction of test

which is unexpected too.

Answer 1

[Titus Edelhofer]

Oliver,

what about this:

feval(evalin('base', '@(x) help(x)'), 'help')

This works fine. And as you noted yourself, using {:} you can expand the input variable as cell array.

Titus

Answer 2

[Philip Borghesani]

There is a much simpler solution to this:

 function fh=test
    fh=str2func('@(x) help(x)');
    fh('help')
 end
 ...

str2func isolates any anonymous function created from the surrounding environment see Loren's Blog

[Oliver Woodford]

Nice! Thanks, Phil. I find it bizarre that str2func finds a different function depending on whether you use the anonymous function syntax or just the function name, though.

Answer 3

[Titus Edelhofer]

Hi Oliver,

although this is not an answer to your question it might help anyway: this is one of the reasons to use function handles instead of strings denoting functions. The big advantage of a function handle is, that the function is determined in the moment the function handle in contrast to strings, where in the moment of evaluation the dispatching happens.

If you pass @help instead of 'help' to your function as input, you are sure, that the correct function is used.

Titus

[Oliver Woodford]

Thanks, Titus. I know about function handles, but in my case they won't work. My function is compiling a mex file. The mex file has an associated m file which contains the information required to compile the mex. So depending on whether the mex file has been compiled, calling the function by name will call either the m file or the mex file. This is the desired effect. Using a handle would not allow this to work.

[Titus Edelhofer]

Hm, so renaming the subfunctions to something highly unlikely to be of the same name as outside function does not work either :(.

[Titus Edelhofer]

Oliver,

what about this:

feval(evalin('base', '@(x) help(x)'), 'help')

This works fine. The "only" drawback: you need to know the number of input and output variables to build up the string ...

Titus

[Oliver Woodford]

The unlikely function name thing is a workaround which I can use. I'm hoping I won't need to, though. I can use the solution above :). Although the number of input arguments aren't known, I can put them in a cell array:

 feval(evalin('base', '@(x) help(x{:})'), {'help'})

If you make it an answer I'll accept it.

[Alfonso Nieto-Castanon]

couldn't you use:

 feval(evalin('base','@(varargin) help(varargin{:})'),'help')

to account for variable number of inputs?