Represents a shared context for randomized runners.

context () creates a new context for randomized runners. The context should be consumed by a call of run ~context ....

runner_on_this_thread context starts a runner on the current thread to run fibers on the context. The runner returns when run ~context ... returns.

run main runs the main thunk with the scheduler. Returns after main and all of the fibers spawned by main have returned.

The optional context argument specifies a context in which to run the main thunk. If unspecified, a new context is automatically created and the scheduler will be single-threaded. By creating a context, spawning concurrent or parallel runners on to the context, and then explicitly passing the context to run ~context ... one can create a multi-threaded scheduler. Only a single call of run per context is allowed.

The optional forbid argument defaults to false and determines whether propagation of cancelation is initially allowed.