A value protected by a mutex

Create a new protected value.

with_ l f runs f x where x is the value protected with the lock l, in a critical section. If f x fails, with_lock l f fails too but the lock is released.

update l f replaces the content x of l with f x, while protected by the mutex.

update_map l f computes x', y = f (get l), then puts x' in l and returns y, while protected by the mutex.

Underlying mutex.

Atomically get the value in the lock. The value that is returned isn't protected!

Atomically set the value.

NOTE caution: using get and set as if this were a ref is an anti pattern and will not protect data against some race conditions.