fix mapVectorM(_) and add example

1 files changed, 42 insertions, 0 deletions

diff --git a/examples/vector-map.hs b/examples/vector-map.hs
new file mode 100644
index 0000000..d778358
--- /dev/null
+++ b/examples/vector-map.hs
@@ -0,0 +1,42 @@
+-- use of vectorMapM
+--
+
+-------------------------------------------
+
+import Data.Packed.Vector
+import Numeric.LinearAlgebra.Interface
+
+import Control.Monad.State
+import Control.Monad.Trans
+
+-------------------------------------------
+
+-- an instance of MonadIO, a monad transformer
+type VectorMonadT = StateT Int IO
+
+v :: Vector Int
+v = fromList $ take 10 [0..]
+
+test1 :: Vector Int -> IO (Vector Int)
+test1 = do
+        mapVectorM (\x -> do
+                          putStr $ (show) x ++ " "
+                          return (x + 1))
+                            
+-- we can have an arbitrary monad AND do IO
+addInitialM :: Vector Int -> VectorMonadT ()
+addInitialM = mapVectorM_ (\x -> do
+                                 i <- get
+                                 liftIO $ putStr $ (show $ x + i) ++ " "
+                                 put $ x + i
+                          )
+
+-------------------------------------------
+main = do
+       v' <- test1 v
+       putStrLn ""
+       putStrLn $ show v'
+       evalStateT (addInitialM v) 1
+       putStrLn ""
+       return ()
+