From df7d0f93d38f229ea6cdd8e391480c3f5b085af5 Mon Sep 17 00:00:00 2001
From: Yann Herklotz <ymherklotz@gmail.com>
Date: Sun, 28 Oct 2018 22:53:38 +0000
Subject: Random generation of trees

---
 src/Main.hs | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/Main.hs b/src/Main.hs
index e25986c..0d49a3c 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -1,9 +1,9 @@
 module Main where
 
 import Data.Bits
+import Test.QuickCheck hiding ((.&.), (.|.))
 
-newtype Input = Input { getInput :: Bool }
-              deriving (Show)
+type Input = Bool
 
 data Gate = And
           | Or
@@ -12,12 +12,22 @@ data Gate = And
           | Nor
           deriving (Show)
 
-data Circuit = In Input
-             | Node Gate Circuit Circuit
-             deriving (Show)
+data Circuit a = In a
+               | Node Gate (Circuit a) (Circuit a)
+               deriving (Show)
 
-eval :: Circuit -> Bool
-eval (In val) = getInput val
+instance Arbitrary Gate where
+  arbitrary = elements [And, Or, Xor, Nand, Nor]
+
+instance (Arbitrary a) => Arbitrary (Circuit a) where
+  arbitrary = do
+    x <- arbitrary
+    frequency [(1, return (In x)), (1, arbNode)]
+      where
+        arbNode = Node <$> arbitrary <*> arbitrary <*> arbitrary
+
+eval :: (Bits a) => Circuit a -> a
+eval (In val) = val
 eval (Node And c1 c2) = eval c1 .&. eval c2
 eval (Node Or c1 c2) = eval c1 .|. eval c2
 eval (Node Xor c1 c2) = eval c1 `xor` eval c2
@@ -25,4 +35,4 @@ eval (Node Nand c1 c2) = complement $ eval c1 .&. eval c2
 eval (Node Nor c1 c2) = complement $ eval c1 .|. eval c2
 
 main :: IO ()
-main = print . eval $ Node And (In . Input $ True) (In . Input $ True)
+main = sample (arbitrary :: Gen (Circuit Input))
-- 
cgit