Unable to define discrete system

[tpunnoose]

In order to minimize the number of continuous dynamics calls for my linear system, I have tried to implement my own custom integration type and discrete_dynamics functions. However, I still have to define a continuous dynamics function because the initialization rollout defaults to the default integration rule. The following lines of code seem to be the culprit:

https://github.com/RoboticExplorationLab/Altro.jl/blob/a33a013c28c6fdcc35dbc48ba02e0e372a56e995/src/ilqr/rollout.jl#L33

TrajectoryOptimization.jl/src/trajectories.jl

Line 178 in 20f726e

RobotDynamics.propagate_dynamics(DEFAULT_Q, model, Z[k], Z[k-1])

This currently prevents you from defining a purely discrete system.