From 4bade78170769d8f26ff709c69cfa4f37341a466 Mon Sep 17 00:00:00 2001
From: Jan Sucan <jan@jansucan.com>
Date: Sun, 26 Oct 2025 20:47:53 +0100
Subject: 24_b_1, 24_b_2: Add solution

---
 ch24/Sorting.hs | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 ch24/Sorting.hs

(limited to 'ch24/Sorting.hs')

diff --git a/ch24/Sorting.hs b/ch24/Sorting.hs
new file mode 100644
index 0000000..6fb9870
--- /dev/null
+++ b/ch24/Sorting.hs
@@ -0,0 +1,56 @@
+{-- snippet parSort --}
+module Sorting where
+
+import Control.Parallel (par, pseq)
+
+parSort :: (Ord a) => [a] -> [a]
+parSort (x:xs)    = force greater `par` (force lesser `pseq`
+                                         (lesser ++ x:greater))
+    where lesser  = parSort [y | y <- xs, y <  x]
+          greater = parSort [y | y <- xs, y >= x]
+parSort _         = []
+{-- /snippet parSort --}
+
+{-- snippet sillySort --}
+sillySort (x:xs) = greater `par` (lesser `pseq`
+                                  (lesser ++ x:greater))
+    where lesser   = sillySort [y | y <- xs, y <  x]
+          greater  = sillySort [y | y <- xs, y >= x]
+sillySort _        = []
+{-- /snippet sillySort --}
+
+{-- snippet sort --}
+sort :: (Ord a) => [a] -> [a]
+sort (x:xs) = lesser ++ x:greater
+    where lesser  = sort [y | y <- xs, y <  x]
+          greater = sort [y | y <- xs, y >= x]
+sort _ = []
+{-- /snippet sort --}
+
+{-- snippet seqSort --}
+seqSort :: (Ord a) => [a] -> [a]
+seqSort (x:xs) = lesser `pseq` (greater `pseq`
+                                (lesser ++ x:greater))
+    where lesser  = seqSort [y | y <- xs, y <  x]
+          greater = seqSort [y | y <- xs, y >= x]
+seqSort _ = []
+{-- /snippet seqSort --}
+
+{-- snippet force --}
+force :: [a] -> ()
+force xs = go xs `pseq` ()
+    where go (_:xs) = go xs
+          go [] = 1
+{-- /snippet force --}
+
+{-- snippet parSort2 --}
+parSort2 :: (Ord a) => Int -> [a] -> [a]
+parSort2 d list@(x:xs)
+  | d <= 0     = sort list
+  | otherwise = force greater `par` (force lesser `pseq`
+                                     (lesser ++ x:greater))
+      where lesser      = parSort2 d' [y | y <- xs, y <  x]
+            greater     = parSort2 d' [y | y <- xs, y >= x]
+            d' = d - 1
+parSort2 _ _              = []
+{-- /snippet parSort2 --}
-- 
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