MATLAB Answers


Can I overwrite a function in a compiled program with a custom version?

Asked by Zhangxi Feng on 1 Jul 2019
Latest activity Commented on by Zhangxi Feng on 2 Jul 2019
Accepted Answer by Jan
I have a set of MATLAB functions with a main function that will be compiled. This program calls a function that requires the user to design part of it.
For example, I have a compiled program runFit.exe. The source code calls a wrapper.m that gets some parameters which the user defines how the parameters are actually used. I would need to include wrapper.m when I compile runFit.exe, but can the user write a new wrapper.m that gets used instead of the one compiled in the code? Or is the only way is to not compile the program?


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1 Answer

Answer by Jan
on 1 Jul 2019
 Accepted Answer

This will not work. And if it works, it would conflict with the license conditions.
Do not provide parameters as M-functions, but as data files, e.g. in text format, as binary or MAT file. Then it is easy to let the user change the parameters without the need to parse and run an M-function.


@Zhangxi Fend: It is a good programming practice to keep code for computations and input data separated. It is a standard for scientific software, that inputs can be provided by text or binary files. The ini files under Windows and the configuration files of Linux systems are famous examples. As soon, as the data are not included in a specific code, e.g. as Matlab code, it is possible in theory, to process them with different tools and to compare the results.
You can create your own file format and a Matlab function to import it. You can implement all kind of special cases, e.g. the number of parameters or of the needed files to be imported. There is no need to implement this as Matlab code, because these cases are such simple, that some simple tables are sufficient. This is even a good idea, if you do not compile the code. A strictly defined import functions is more reliable that creating a set of different codes to create the input data, because code must be tested exhaustively in every case. Even trivial code offers an infinite number of possible bugs. So prefer to write one code and test it exhaustively and provide the data as dull and static text/binary files.
For example, some times it may need to write more parameters, sometimes less, and sometimes may need to write more than one file.
While allowing user to specify all this as matlab code may be the easiest for now, it's also the most fragile. The user have to be careful not to stomp over your own variables with their m code (maybe they're not even aware of your own variables, and one day a user overwrites one of your variable which slightly changes the behaviour of the code and results in slightly incorrect outputs. That goes unnoticed until the probe crashes into Mars because it's off by a few 100 meters).
The correct way to deal with this is to provide an input method completely independent of m code that allows for all these variations. It could be via configuration, a GUI, whatever. Yes, it'll be more work to start with, but ultimately a better usage experience.
Thank you for your suggestions. I can definitely see a way to design an input file reader that dynamically recognizes the user's desired parameters and writes them according to the user's given conditions to achieve the level of flexibility for this.

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