# WRAP

The wrap library wraps the GTSAM library into a Python library or MATLAB toolbox.
It was designed to be more general than just wrapping GTSAM. For notes on creating a wrap interface, see `gtsam.h` for what features can be wrapped into a toolbox, as well as the current state of the toolbox for GTSAM.

## Prerequisites: Pybind11 and pyparsing

1. This library uses `pybind11`, which is included as a subdirectory in GTSAM.
2. The `interface_parser.py` in this library uses `pyparsing` to parse the interface file `gtsam.h`. Please install it first in your current Python environment before attempting the build.
    ```
    python3 -m pip install pyparsing
    ```

## GTSAM Python wrapper

**WARNING: On macOS, you have to statically build GTSAM to use the wrapper.**

1. Set `GTSAM_BUILD_PYTHON=ON` while configuring the build with `cmake`.
1. What you can do in the `build` folder:
    1. Just run python then import GTSAM and play around:
        ```

        import gtsam
        gtsam.__dir__()
        ```

    1. Run the unittests:
        ```
        python -m unittest discover
        ```
    1. Edit the unittests in `python/gtsam/*.py` and simply rerun the test.
    They were symlinked to `<build_folder>/gtsam/*.py` to facilitate fast development.
        ```
        python -m unittest gtsam/tests/test_Pose3.py
        ```
        - NOTE: You might need to re-run `cmake ..` if files are deleted or added.
1. Do `make install` and `cd <gtsam_install_folder>/python`. Here, you can:
    1. Run the unittests:
        ```
        python setup.py test
        ```
    2. Install `gtsam` to your current Python environment.
        ```
        python setup.py install
        ```
        - NOTE: It's a good idea to create a virtual environment otherwise it will be installed in your system Python's site-packages.


## Old GTSAM Wrapper

*Outdated note from the original wrap.*

TODO: Update this.

It was designed to be more general than just wrapping GTSAM, but a small amount of GTSAM specific code exists in `matlab.h`, the include file that is included by the `mex` files. The GTSAM-specific functionality consists primarily of handling of Eigen Matrix and Vector classes.

For notes on creating a wrap interface, see `gtsam.h` for what features can be wrapped into a toolbox, as well as the current state of the toolbox for GTSAM. For more technical details on the interface, please read comments in `matlab.h`

Some good things to know:

OBJECT CREATION

- Classes are created by special constructors, e.g., `new_GaussianFactorGraph_.cpp`.
	These constructors are called from the MATLAB class `@GaussianFactorGraph`.
	`new_GaussianFactorGraph_` calls wrap_constructed in `matlab.h`, see documentation there

METHOD (AND CONSTRUCTOR) ARGUMENTS

- Simple argument types of methods, such as "double", will be converted in the
  `mex` wrappers by calling unwrap<double>, defined in matlab.h
- Vector and Matrix arguments are normally passed by reference in GTSAM, but
  in `gtsam.h` you need to pretend they are passed by value, to trigger the
  generation of the correct conversion routines `unwrap<Vector>` and `unwrap<Matrix>`
- passing classes as arguments works, provided they are passed by reference.
	This triggers a call to unwrap_shared_ptr