4.3 Cooperative Threads

To use cooperative threads, create a threading context with call-in-main-thread, and perform thread operations—such as creating a new thread with thread or a channel with channel—during the body of the thunk provided to call-in-main-thread. Threads can block either on channels or on a process handle as from process. Only one thread runs at a time, where a thread switch happens only when a thread terminates or uses a (potentially) blocking operation.

Except for thread? and channel?, these procedures can be used only in a threading context. A channel can be used only in the threading context where it was created.

Beware that attempting to use these operations outside of a threading context will not necessarily trigger an error, and may instead deliver an opaque threading request to the enclosing continuation prompt.