Unbias a random generator: Difference between revisions

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 =={{header|Haskell}}==
+The first task:
 <lang haskell>import Control.Monad.Random
 import Control.Monad
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 randN :: MonadRandom m => Int -> m Int
-randN n = fromList [(0, fromIntegral n-1), (1, 1)]
+randN n = fromList [(0, fromIntegral n-1), (1, 1)]</lang>
+Examples of use:
--- works for any random generator
+<pre>λ> replicateM 20 (randN 2)
-unbias :: (MonadRandom m, Eq x) => m x -> m x
+[0,0,1,0,0,1,0,1,1,0,0,1,1,1,1,0,1,1,0,0]
-unbias g = do x <- g
+λ> replicateM 20 (randN 5)
+[0,1,0,0,0,0,0,0,1,0,0,0,0,1,0,0,1,0,1,0]</pre>
+The second task. Returns the unbiased generator for any given random generator.
+<lang Haskell>unbiased :: (MonadRandom m, Eq x) => m x -> m x
+unbiased g = do x <- g
               y <- g
-              if x /= y then return y else unbias g
+              if x /= y then return y else unbias g</lang>
+Examples of use:
+<pre>λ> replicateM 20 (unbiased (randN 5))
+[0,0,1,0,1,1,1,0,0,0,1,1,1,0,1,1,0,0,1,0]
+λ> replicateM 20 (unbias (fromList [(True,10),(False,1)]))
+[True,True,False,True,True,True,False,True,False,True,True,False,False,True,False,True,True,False,False,True]</pre>
+The third task:
-main = forM_ [3..6] showCounts
+<lang Haskell>main = forM_ [3..6] showCounts
   where
     showCounts b = do