instances for Integer and Bool

Frege · Nov 6, 2013 · 6b54457 · 6b54457
1 parent bc52881
commit 6b54457
Showing 1 changed file with 32 additions and 9 deletions.
diff --git a/frege/lib/Random.fr b/frege/lib/Random.fr
@@ -11,12 +11,14 @@ package frege.lib.Random where
     class RandomGen g where
         next     :: g -> (Int, g)
         nextLong :: g -> (Long, g)
+        nextBool :: g -> (Bool, g)
+        nextDouble :: g -> (Double, g)
         split    :: g -> (g,g)
         genRange :: g -> (Int, Int)
         genRange _ = (Int.minBound, Int.maxBound)
 
 
-    private data JavaGen = native java.util.Random where
+    protected data JavaGen = native java.util.Random where
         public  native new         :: ()   -> IOMutable JavaGen
                                    |  Long -> STMutable s JavaGen
         public  native nextInt     :: Mutable s JavaGen -> ST s Int
@@ -27,22 +29,21 @@ package frege.lib.Random where
 
     abstract data StdGen = StdGen Long where
         new i = StdGen (Int.long i)
-        private nextST (StdGen seed) = do
+        private nextST (StdGen seed) next = do
                 r <-JavaGen.new seed
-                i <- JavaGen.nextInt r
+                i <- next r
                 l <- JavaGen.nextLong r
                 return (i, StdGen l)
         -- get the next integer and a new generator
-        next g = ST.run (g.nextST)
+        next g = ST.run (nextST g JavaGen.nextInt)
         -- i have no idea if this works
         split (g@StdGen seed) = (g0, g1) where
                 (!i,!g1) = next g
                 !g0 = StdGen (seed + i.long)
-        nextLong (StdGen seed) = ST.run do
-                r <- JavaGen.new seed
-                l1 <- JavaGen.nextLong r
-                l2 <- JavaGen.nextLong r
-                return (l1, StdGen l2)
+        nextLong (g@StdGen seed) = ST.run (nextST g JavaGen.nextLong)
+        nextBool (g@StdGen seed) = ST.run (nextST g JavaGen.nextBool)
+        nextDouble (g@StdGen seed) = ST.run (nextST g JavaGen.nextDouble)
+
 
     instance RandomGen StdGen
 
@@ -97,3 +98,25 @@ package frege.lib.Random where
                     n = abs (i `mod` r) + l
                     !g0 = (n `band` 0xffffffffL).int
                 in (g0, g1)
+
+    instance Random Integer where
+        {--
+            We allow only intervals from (Long.minBound `div` 2)
+            to (Long.maxBound `div` 2) with the exception (Long.minBound, Long.maxBound),
+            which is allowed.
+        -}
+        randomR (lower,upper) g
+           | Long.minBound.big == lower && Long.maxBound.big == upper = case g.nextLong of
+                (a, g) -> case g.nextLong of
+                    (b, g) -> case g.nextLong of
+                        (c, g) -> case g.nextLong of
+                            (d, g) -> ((a.big+b.big) * (c.big-d.big), g)
+
+           | otherwise = case g.nextLong of
+                (n, g) -> (abs n.big `rem` (upper-lower) + lower, g)
+
+        random g = randomR (Long.minBound.big, Long.maxBound.big) g
+
+    instance Random Bool where
+        random g = randomR (false, true) g
+        randomR (_,_) g = g.nextBool