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| Control.Concurrent.SampleVar |
|
| type SampleVar a = MVar (Int, MVar a) |
| newEmptySampleVar :: IO (SampleVar a) |
| newSampleVar :: a -> IO (SampleVar a) |
| emptySampleVar :: SampleVar a -> IO () |
| readSampleVar :: SampleVar a -> IO a |
| writeSampleVar :: SampleVar a -> a -> IO () |
Sample variables are slightly different from a normal MVar:
Reading an empty SampleVar causes the reader to block. (same as takeMVar on empty MVar)
Reading a filled SampleVar empties it and returns value. (same as takeMVar)
Writing to an empty SampleVar fills it with a value, and potentially, wakes up a blocked reader (same as for putMVar on empty MVar).
Writing to a filled SampleVar overwrites the current value. (different from putMVar on full MVar.)