Control.Concurrent.STM.Counter

The Counter module implements a thread-safe integer counter. It can be used to generate unique ids in a multi-threaded system.

Documentation

type Counter = IORef Int

The counter is implemented as a simple IORef and modified atomically.

getCounter :: Counter

Returns a global counter.

incr :: Counter -> IO ()

Increments the counter.

get :: Counter -> IO Int

Returns the current value of the counter.

getAndIncr :: Counter -> IO Int

Increments the counter and returns the previous version.