A monad for interacting with Hardcaml.Cyclesim based simulations.
Multiple control threads can be spawned and can wait_for child
threads to complete.
Synchronisation between threads is performed at every clock cycle.
There are separate versions for the cyclesim and event_driven_sim simulators.
Further, two styles of writing testbenches are provided: functional and imperative.
In the functional style new values for simulation input ports are collected, the simulation updated, and outputs distributed amoung the control threads.
In the imperative style testbench writers just access the simulator ports directly.