Call a function that is not on the Matlab path WITHOUT ADDING THAT PATH

Question

I have been searching an entire afternoon and have found no solution to call in matlab a function by specifying its path and not adding its directory to the path.

This question is quite similar to Is it possible to call a function that is not in the path in MATLAB?, but in my case, I do not want to call a built-in function, but just a normal function as defined in an m-file.

I think handles might be a solution (because apparently they can refer to functions not on the path), but I again found no way to create a handle without cd-ing to the directory, creating it there and the cd-ing back. Trying to 'explore' what a function handle object is and how to make one with a reference to a specific function not on the path has led me nowhere.

So the solution might come from two angles:
1) You know how to create a handle for an m-file in a specific directory.
2) You know a way to call a function not on the matlab path.

EDIT: I have just discovered the function functions(myhandle) which actually lets you see the filepath to which the handle is referring. But still no way to modify it though...

Answer 1

This is doable, but requires a bit of parsing, and a call to evalin.

I added (many years ago!) a function to the MATLAB Central File Exchange called externalFcn

http://www.mathworks.com/matlabcentral/fileexchange/4361-externalfcn

that manages calls to off-path functions. For instance, I have a function called offpathFcn that simply returns a structure with a success message, and the value of an input. Storing that function off my MATLAB path, I can call it using:

externalfcn('out = C:\MFILES_OffPath\offpathFcn(''this is a test'')');

This returns:

out = 
    success: 1
    input: 'this is a test'

(Note that my implementation is limited, and improvable; you have to include an output with an equal sign for this to work. But it should show you how to achieve what you want.)

(MathWorks application engineer)

Answer 2

The solution as noted in the comment 1 to create a function handle before calling the function is nicely implemented by @Rody Oldenhuis' FEX Contribution: http://www.mathworks.com/matlabcentral/fileexchange/45941-constructor-for-functionhandles