[Haskell-beginners] How to display a time difference?
sean.ysl at gmail.com
Wed Mar 18 06:54:09 EDT 2009
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
<colin at colina.demon.co.uk> wrote:
>>>>>> "Sean" == Sean Lee <sean.ysl at gmail.com> 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
> 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
Programming Language and Systems Research Group
School of Computer Science and Engineering
University of New South Wales
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