Documentation

Create a new semaphore with the given argument as the initially available quantity. This allows new semaphores to start with a negative, zero, or positive quantity.

It is recommended that all paired uses of wait and signal use the with bracketed form to ensure exceptions safety.

Try to take a unit of value from the semaphore. This succeeds when the current quantity is positive, and then reduces the quantity by one. Otherwise this will block and retry until it succeeds or is killed. This will never result in a negative quantity. If several threads are retying then which one succeeds next is undefined -- an unlucky thread might starve.

Signal that single unit of the semaphore is available. This increases the available quantity by one.

Non-waiting version of wait. `tryWait s` is defined as `tryWaitN s 1`

It is recommended that all paired uses of waitN and signalN use the withN bracketed form to ensure exceptions safety.

Try to take the given value from the semaphore. This succeeds when the quantity is greater or equal to the given value, and then subtracts the given value from the quantity. Otherwise this will block and retry until it succeeds or is killed. This will never result in a negative quantity. If several threads are retrying then which one succeeds next is undefined -- an unlucky thread might starve.

Signal that many units of the semaphore are available. This changes the available quantity by adding the passed size.

Non-waiting version of waitN. It either takes the quantity from the semaphore like waitN and returns `Just value taken` or finds insufficient quantity to take and returns Nothing

This returns the current quantity in the semaphore. This is diffucult to use due to race conditions.