The type of binary semaphores.

make b returns a new binary semaphore. If b is true, the initial value of the semaphore is 1, meaning "available". If b is false, the initial value of the semaphore is 0, meaning "unavailable".

release s sets the value of semaphore s to 1, putting it in the "available" state. If other threads are waiting on s, one of them is restarted.

acquire s blocks the calling thread until the semaphore s has value 1 (is available), then atomically sets it to 0 and returns.

try_acquire s immediately returns false if the semaphore s has value 0. If s has value 1, its value is atomically set to 0 and try_acquire s returns true.