Add example

examples/BinaryTree.hs

@@ -0,0 +1,24 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+module BinaryTree where
+
+import Data.Data
+import Data.Random.Generics
+
+data T = N T T | L
+  deriving (Eq, Ord, Show, Data)
+
+-- size
+s :: T -> Integer
+s (N l r) = 1 + s l + s r
+s L = 1
+
+mBoltz :: IO T
+mBoltz = makeGenerator randomPrimRandom undefined 0 10
+
+-- Pointing makes the generator more precise.
+mPoint :: IO T
+mPoint = makeGenerator randomPrimRandom undefined 1 10
+
+-- Rejection is more elementary and works fine too.
+mReject :: IO T
+mReject = randomGenerator 10