MATLAB Wrapper Does Not Support Default Arguments

[mattking-smith]

Description

It appears that the wrapper definitions generated when binding GTSAM to MATLAB need additional arguments then the default arguments provided for the MATLAB examples.

Steps to reproduce

1. Install GTSAM + MATLAB toolbox..
2. In the MATLAB environment attempt the following:

cd /Users/yourname/toolbox % Change to wherever you installed the toolbox
cd gtsam_examples % Change to the examples directory
gtsamExamples % Run the GTSAM examples GUI

Expected behavior

Successful completion of program

Observed behavior

I am seeing that errors when testing all the GTSAM examples in the gtsam_examples folder.

For example when looking at StereoVOExample.m when trying to execute
stereo_model = noiseModel.Isotropic.Sigma(3,1);
as written when compiled throws the error:

>> stereo_model = noiseModel.Isotropic.Sigma(3,1);
Error using gtsam.noiseModel.Isotropic.Sigma (line 76)
Arguments do not match any overload of function
Isotropic.Sigma

However looking at the wrapper definition under Isotropic.m states
%Sigma(size_t dim, double sigma, bool smart) : returns gtsam::noiseModel::Isotropic
where the Isotropic wrapper definition in MATLAB is:

    function varargout = Sigma(varargin)
      % SIGMA usage: Sigma(size_t dim, double sigma, bool smart) : returns gtsam.noiseModel.Isotropic
      % Doxygen can be found at https://gtsam.org/doxygen/
      if length(varargin) == 3 && isa(varargin{1},'numeric') && isa(varargin{2},'double') && isa(varargin{3},'logical')
        varargout{1} = gtsam_wrapper(1092, varargin{:});
        return
      end

      error('Arguments do not match any overload of function Isotropic.Sigma');
    end

Hence executing
>> stereo_model = noiseModel.Isotropic.Sigma(3,1,true);
is handled without error and GTSAM can properly optimize the StereoVOExample.m file:

Optimizing
Elapsed time is 0.014737 seconds.

Conclusion

It appear that some wrapper definitions have changed and the baseline example codes in MATLAB need to updated to reflect this, or the wrapper needs to be updated as to accommodate baseline default arguments.

Environment

MATLAB version: 2021a
Linux OS: Ubuntu 20.04
Standard GTSAM + MATLAB Toolbox build.

Originally posted by @mattking-smith in #953 (review)

[dellaert]

This is the default argument issue: I think previously there were wt versions of the Sigma function: one with 2 arguments and one with 3. This was then replaced with one, with a default argument, but that (silently) broke the MATLAB examples. A quick fix, @mattking-smith , if you're up for it, is to push a quick PR with the "true" argument added in all examples that fail. Then we can take a bit more time fixing the wrapper code - and as I alluded to, it might be beneficial for you to be involved in that more permanent fix.

[mattking-smith]

This is the default argument issue: I think previously there were wt versions of the Sigma function: one with 2 arguments and one with 3. This was then replaced with one, with a default argument, but that (silently) broke the MATLAB examples. A quick fix, @mattking-smith , if you're up for it, is to push a quick PR with the "true" argument added in all examples that fail. Then we can take a bit more time fixing the wrapper code - and as I alluded to, it might be beneficial for you to be involved in that more permanent fix.

Yeah I can do this to give a quick fix a go.

[mattking-smith]

Yeah I can do this to give a quick fix a go.

As I am working on this I have been able to fix simple bugs, like adding true to >> stereo_model = noiseModel.Isotropic.Sigma(3,1,true);, but I am struggling to fix the graph.print() feature of a MATLAB-based graph, which is called in many examples.

For example in the LocalizationExample.m file, the command
graph.print(sprintf('\nFactor graph:\n')); results in the error

Error using gtsam.NonlinearFactorGraph/print (line 406)
Arguments do not match any overload of function gtsam.NonlinearFactorGraph.print

The print function is defined in the NonlinearFactorGraph.m file as

    function varargout = print(this, varargin)
      % PRINT usage: print(string s, KeyFormatter keyFormatter) : returns void
      % Doxygen can be found at https://gtsam.org/doxygen/
      if length(varargin) == 2 && isa(varargin{1},'char') && isa(varargin{2},'gtsam.KeyFormatter')
        gtsam_wrapper(1575, this, varargin{:});
        return
      end
      error('Arguments do not match any overload of function gtsam.NonlinearFactorGraph.print');
    end

The new additional argument here is the 'gtsam.KeyFormatter'. I am struggling to find an example on how to create a KeyFormatter for this function in the MATLAB environment. @gchenfc do you have any thoughts on how I could generate the KeyFormatter in MATLAB for the print command?

[dellaert]

If it is limited to one or two classes, you can always add the two versions of the function back into the wrapper, ie One with the KeyFormatter and one without. Then the default argument will be selected in C++

[mattking-smith]

@varunagrawal, I believe once the master version of the wrapper library is merged into this repository we can close this issue.

[varunagrawal]

Yeah I'm already on that :)