It leaks with me too.
It's the same problem I'm having with my Pong attempt (see my post http://www.haskell.org/pipermail/reactive/2010-May/000337.html)

The more often the integration event ticks, the quicklier the program time-leaks.

I'm also using reactive 0.11.4 and GHC 6.12.1.
I'm running Ubuntu 9.10 64bits version.
Doesn't matter whether I use -O2 or not.


> Hi folks,

> I've got stacked now because of a time leak problem with integral. 
> The following program leaks CPU-time gradually:

> import FRP.Reactive
> import FRP.Reactive.LegacyAdapters

> import Control.Applicative

> type Velocity = Double
> type Position = Double

> data Car = Car { vel :: Velocity, pos :: Position } deriving Show

> velocity :: Behavior Velocity

> velocity = 1

> position :: Behavior Position
> position = integral (atTimes [0, 0.5 ..]) velocity

> car :: Behavior Car
> car = Car <$> velocity <*> position


> main :: IO ()
> main = adaptE $ print <$> car `snapshot_` atTimes [0, 0.5..]

> 1) why is the leak happen?
> 2) how can I fix this problem?

> Some more detailed informations:

> * reactive 0.11.4
> * GHC 6.12.1
> * Gentoo Linux (2.6.32-tuxonice, x86_64)
> * compiled with or without -O2 flag

> Thanks,
> -- 
> Mitsutoshi Aoe