Changeset 14926 for src/Pugs/Prim/List.hs

Timestamp:

12/19/06 00:15:47 (2 years ago)

Author:

luqui

Message:

Made pick faster.

Files:

• src/Pugs/Prim/List.hs (modified) (2 diffs)

src/Pugs/Prim/List.hs

@@ -59 +59 @@
 op1Pick v = retError "pick not defined" v
 
-shuffle :: [a] -> Eval [a]
-shuffle [] = return []
-shuffle xs = do
+shuffleN :: Int -> [a] -> Eval [a]
+shuffleN _ [] = return []
+shuffleN 0 _  = return []
+shuffleN n xs = do
     -- pick the first element
     first <- liftIO $ randomRIO (0 :: Int, length xs - 1)
-    rest <- shuffle $ take first xs ++ drop (first+1) xs
+    rest <- shuffleN (n-1) $ take first xs ++ drop (first+1) xs
     return $ head (drop first xs) : rest
 
@@ -72 +73 @@
     op2Pick ref num
 op2Pick (VList xs) (VInt num) = do
-    shuffled <- shuffle xs
-    return $ VList $ take (fromInteger num) shuffled
+    shuffled <- shuffleN (fromInteger num) xs
+    return $ VList shuffled
 op2Pick r _ = retError "pick not defined" r