Re: [Haskell-beginners] How to display a time difference?

Am Mittwoch, 18. März 2009 11:54 schrieb Sean Lee:

You get some random values? or no change at all on the state?

On Wed, Mar 18, 2009 at 9:45 PM, Colin Paul Adams

wrote:

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> "Sean" == Sean Lee writes:

Sean> Hi Colin The following code probably would do what I wanted Sean> to do.

Sean> play_move :: IORef Game_state -> IO () play_move Sean> game_state_ior = do (_, state, _) <- readIORef Sean> game_state_ior putStr "Playing AI: " start_time <- Sean> getCurrentTime let move = recommended_move state end_time <- Sean> move `seq` (modifyIORef game_state_ior $! Sean> update_interactive_from_move move) `seq` getCurrentTime

that should probably have been move `seq` (modifyIORef game_state_ior $! ... ) >> getCurrentTime value `seq` ioAction1 `seq` ioAction2 doesn't execute ioAction1.

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Sean> putStrLn $ show $ (diffUTCTime end_time start_time)

Sean> Due to the non-strictness of Haskell, the evaluation of the Sean> expressions between start_time and end_time is deferred Sean> until there is a need. By using `seq` and ($!), the Sean> strictness can be forced.

It certainly causes a time delay, and a non-zero time is printed, but the state doesn't get modified correctly now.

??

I will ponder Daniel's suggestion. -- Colin Adams Preston Lancashire