gistfile1.hs

import qualified Data.Vector.Unboxed.Mutable as M
import qualified Data.Vector.Generic.Mutable as GM
import Control.Monad

type DVector = M.IOVector Double
data Grid = Grid Int DVector

-- |Create an empty vector
emptyGrid :: Int -> IO Grid
emptyGrid sz = do
  d <- GM.unsafeNewWith (vectorLength sz) 0
  return (Grid sz d)

-- |Translate from 2D to 1D co-ordinates
ix :: Int -> (Int,Int) -> Int
ix n (i,j) = i + (n+2) * j

-- |Write a single value at the given co-ordinates
writeVal :: Grid -> (Int,Int) -> Double -> IO ()
writeVal (Grid sz d) p = GM.unsafeWrite d (ix sz p) 

-- |Write multiple values
setVals :: Grid -> [((Int,Int),Double)] -> IO ()
setVals g vals = forM_ vals (uncurry (writeVal g))

-- |Read the value at the given point
readVal :: Grid -> (Int,Int) -> IO Double
readVal (Grid sz d) p = GM.unsafeRead d (ix sz p)