how to implement timeouts for IO operations?

[Johannes Waldmann]

Thank you, Marcin. 

Your reply seems to imply that the structure
of the program I posted was basically OK?


A slightly related point, I was having difficulties with TimeDiff 
values - I got negative tdPicosecs sometimes,
and some functions (show) even dumped core.

Are such problems known (I am using a binary ghc-4.08)?
For the moment, I switched to Posix.EpochTime.


I found TimeDiff and ClockTime quite restrictive:
they are not instances of Num, I can't add/subtract/negate TimeDiffs;
and I cannot generate a zero ClockTime.
(In my application, I need to simulate two clocks,
where always one is running, the other one is stopped -
as used in tournament Chess.)

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