Well, there's the Haskell Array Preprocessor
(http://www.cs.utah.edu/~hal/APP/index.html), but I've never really
used it. I think the first thing to notice is that Control.Monad
really does contain a lot of functions which are useful control
structures. The way that you wrote that loop seems extremely awkward
to me. How I'd write it would be something like:
import Control.Monad
import Data.Array.IO
main = do
a <- (newArray (1,100) 1) :: IO (IOArray Int Int)
forM [2..99] $ \i -> do
v <- liftM2 (+) (readArray a (i-1)) (readArray a (i+1))
writeArray a i v
print =<< getAssocs a
(Note that forM = flip mapM is a recent addition to Control.Monad)
It's possible to go quite a way to cleaning things up just using
appropriate functions.
On 12/12/06, Adam Megacz
Is there any work on automatic translation of code in some tiny imperative language into Haskell code that uses the ST and/or IO monads (or perhaps even pure functional code)?
For example, the user writes something vaguely like
array = newArray (1,100) 1 for x=2 to 99 array[x] := array[x-1]+array[x+1]
And it is transformed into something like
foldl (>>=) (newArray (1,100) 1) $ map (\n arr -> do a <- readArray arr (n-1) b <- readArray arr (n+1) writeArray arr n (a+b) return arr) [2..99]
Obviously the "small imperative language" would have to be highly restricted and carefully chosen in order for the translation to always work and be predictable. I'm interested in any existing work on choosing such a sublanguage.
Thanks!
- a
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