TODO LIST

ROS 2 port
- ROS 2 Foxy Fitzroy (see changes in https://index.ros.org/doc/ros2/Releases/Release-Foxy-Fitzroy/) and Ubuntu 20.04
- more test
- take advantage of discovery (export ROS_DOMAIN_ID=PGCD ?)
frontend
- string constant and other constants are not compatible because of sympy
- parser keep track of positions (line/col) for error messages
- automatically generate frame shift for custom messages (currently limited to some predefined types from geometry package)
type system
- process declaration: name: type
- componenent signature: name, var (id: type)*, mp ( id(arg: type [, arg: type]*) )*
- genration of ROS message signature from decalaration
choreo
- thread partition
  - when traversing and find a fork -> get the paths to the next join
  - find all the processes in each branch and check it is a partition
  - traverse the branches and check all the processes in that branch have MP
- for the compat check, do a product construction directly on the global choreo
- variable duration mp (idle): generalize the causality for time intervals
runtime performance
- have 1 thread for the program/ROS and 1 thread for the motion primitive
- more efficient interaction with tf (apply some code gen rather than sympy all the way, http://www.sympy.org/scipy-2017-codegen-tutorial/)
- interpreter.py, visit_receive and visit_motion: better way to execute motions with messages (spawn a separate thread/process for the motion and interrupt it when done)

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