On 27 May 2010 02:04, Dan Doel
<dan.doel@gmail.com> wrote:
On Wednesday 26 May 2010 5:38:57 pm Pete Chown wrote:
> test :: (Eq a) => (Int -> a) -> (Int -> a) -> Bool
> test f1 f2 = unsafePerformIO $ do
> goodSoFar <- newIORef True
> forLoop 1 100 $ \i ->
> when (f1 i /= f2 i) $ writeIORef goodSoFar False
> readIORef goodSoFar
The problem with this algorithm is that it needlessly tests f1 against f2 for
all i, even when a non-matching value has has already been found. Using the
power of call-with-current-continuation, I have constructed an algorithm that
lacks this deficiency:
import Control.Monad.Cont
test f g = flip runCont id . callCC $ \escape ->
do forM_ [1..100] $ \n ->
when (f n /= g n) $
escape False
return True
This should perform almost 75% less work in the testFunc1 case! It certainly
feels much snappier.
-- Dan