From 939502e5116abe2900740eda48a8eef17e7a154a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20P=C3=A4tzel?= <david.paetzel@posteo.de>
Date: Tue, 22 Oct 2019 06:53:53 +0200
Subject: [PATCH] Add TODOs and comments about shuffle

---
 src/GA.hs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/GA.hs b/src/GA.hs
index 987d476..801926c 100644
--- a/src/GA.hs
+++ b/src/GA.hs
@@ -26,6 +26,19 @@ import Protolude
 import Test.QuickCheck hiding (sample, shuffle)
 import Test.QuickCheck.Instances
 
+-- TODO using sample here was a quick hack
+{-|
+Shuffles a non-empty list.
+-}
+shuffle' :: (MonadRandom m) => NonEmpty a -> m (NonEmpty a)
+shuffle' xs = do
+  i <- sample . uniform 0 $ NE.length xs - 1
+  let x = xs NE.!! i
+  xs' <- sample . shuffle $ deleteI i xs
+  return $ x :| xs'
+  where
+    deleteI i xs = fst (NE.splitAt (i - 1) xs) ++ snd (NE.splitAt i xs)
+
 -- TODO Enforce this being > 0
 type N = Int
 
@@ -130,6 +143,7 @@ children2 nX i1 i2 = do
   i6 <- mutate i4
   return $ i5 :| [i6]
 
+-- TODO there should be some shuffle here
 {-|
 The @k@ best individuals in the population when comparing using the supplied
 function.
@@ -167,6 +181,8 @@ ga' nParents nX pop term nResult = do
       f <- liftIO $ fitness s
       putText $ show f <> "\n" <> pretty s
 
+-- TODO add top x percent selection (select n guys, sort by fitness first)
+
 step
   :: (Individual i, MonadRandom m, Monad m)
   => N