From: Neil Smith <neil.git@njae.me.uk>
Date: Fri, 15 Dec 2017 14:04:23 +0000 (+0000)
Subject: Filtered the modified stream at source, rather than relying on list fusion that didn... 
X-Git-Url: https://git.njae.me.uk/?p=advent-of-code-17.git;a=commitdiff_plain;h=a6809041da3a5cbfd7e55e41c61bcfaa5d3fb1dc

Filtered the modified stream at source, rather than relying on list fusion that didn't happen
---

diff --git a/src/advent15/advent15.hs b/src/advent15/advent15.hs
index 84e2412..5aba6d7 100644
--- a/src/advent15/advent15.hs
+++ b/src/advent15/advent15.hs
@@ -13,8 +13,8 @@ part1 = length $ filter (uncurry (==)) $ take 40000000 $ zip streamA streamB
 
 
 part2 = length $ filter (uncurry (==)) $ take 5000000 $ zip fsA fsB
-    where fsA = filteredStream 3 streamA
-          fsB = filteredStream 7 streamB
+    where fsA = stream' 4 generatorA generatorAStart -- filteredStream 3 streamA
+          fsB = stream' 8 generatorB generatorBStart -- filteredStream 7 streamB
 
 
 generatorA = generator 2147483647 16807
@@ -32,5 +32,10 @@ toWord16 = fromIntegral
 stream :: (Int -> Int) -> Int -> [Word16]
 stream gen n0 = map toWord16 $ drop 1 $ iterate gen n0
 
-filteredStream :: Word16 -> [Word16] -> [Word16]
-filteredStream f = filter ((== 0) . ( .&. f))
+stream' :: Int -> (Int -> Int) -> Int -> [Word16]
+stream' f gen n0 = map toWord16 $ drop 1 $ filter ((== 0) . (`mod` f)) $ iterate gen n0
+
+
+-- filteredStream :: Word16 -> [Word16] -> [Word16]
+-- filteredStream f = filter ((== 0) . ( .&. f))
+