From: Camil Staps <info@camilstaps.nl>
Date: Sat, 18 Apr 2015 13:34:17 +0000 (+0200)
Subject: fp2-w1: RandomGetallen
X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=d944842f1ee00d6e919d52b47798a7788477eb29;p=fp1415.git

fp2-w1: RandomGetallen
---

diff --git a/fp2/week1/camil/RandomGetallen.dcl b/fp2/week1/camil/RandomGetallen.dcl
new file mode 100644
index 0000000..2ca4b27
--- /dev/null
+++ b/fp2/week1/camil/RandomGetallen.dcl
@@ -0,0 +1,7 @@
+definition module RandomGetallen
+
+import Random
+
+random_n	:: Int RandomSeed -> ([Int],RandomSeed)
+random_inf	::     RandomSeed ->  [Int]
+shuffle		:: [a] RandomSeed ->  [a]
diff --git a/fp2/week1/camil/RandomGetallen.icl b/fp2/week1/camil/RandomGetallen.icl
new file mode 100644
index 0000000..a0a21bf
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+++ b/fp2/week1/camil/RandomGetallen.icl
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+implementation module RandomGetallen
+
+import StdEnv, Random
+
+random_n :: Int RandomSeed -> ([Int],RandomSeed)
+random_n 0 seed = ([], seed)
+random_n n seed = ([r:rs], s`)
+where 
+	(rs,s`) = random_n (n-1) s
+	(r,s) = random seed	
+
+random_inf :: RandomSeed -> [Int]
+random_inf s = iterateSt random s
+
+iterateSt :: (s -> (a,s)) s -> [a]
+iterateSt f s = [a : iterateSt f s`]
+where
+	(a,s`) = f s
+
+shuffle :: [a] RandomSeed -> [a]
+shuffle xs s = (perms xs)!!(fst (random s) rem (factorial (length xs)))
+
+perms :: [a] -> [[a]]
+perms [] = [[]]
+perms xs = [[xs!!i : xs`] \\ i <- [0..length xs - 1] , xs` <- perms (take i xs ++ drop (i+1) xs)]
+
+factorial :: Int -> Int
+factorial 0 = 1
+factorial n = n * factorial (n-1)