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File 1445-Improve-list-comprehensions-quicksort-example.patch of Package erlang (Revision b4f72044e1af8cfe32130ab849a401a1)

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From d9687b5546d8b01092baa66375c094ec28b26fd8 Mon Sep 17 00:00:00 2001
From: Maria Scott <maria-12648430@hnc-agency.org>
Date: Tue, 9 Jan 2024 15:22:09 +0100
Subject: [PATCH] Improve list comprehensions quicksort example
MIME-Version: 1.0
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Co-authored-by: Björn Gustavsson <bgustavsson@gmail.com>
---
 .../list_comprehensions.xml | 47 ++++++++++++++-----
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/system/doc/programming_examples/list_comprehensions.xml b/system/doc/programming_examples/list_comprehensions.xml
index 25df0a06bc..cf1b4aadd9 100644
--- a/system/doc/programming_examples/list_comprehensions.xml
+++ b/system/doc/programming_examples/list_comprehensions.xml
@@ -56,26 +56,47 @@
 <title>Quick Sort</title>
 The well-known quick sort routine can be written as follows:
 <code type="none"><![CDATA[
+sort([]) -> [];
+sort([_] = L) -> L;
 sort([Pivot|T]) ->
 sort([ X || X <- T, X < Pivot]) ++
 [Pivot] ++
- sort([ X || X <- T, X >= Pivot]);
-sort([]) -> [].]]></code>
+ sort([ X || X <- T, X >= Pivot]).]]></code>
 The expression <c><![CDATA[[X || X <- T, X < Pivot]]]></c> is the list of
 all elements in <c>T</c> that are less than <c>Pivot</c>.
 <c><![CDATA[[X || X <- T, X >= Pivot]]]></c> is the list of all elements in
 <c>T</c> that are greater than or equal to <c>Pivot</c>.
- A list sorted as follows:
- <list type="bulleted">
- <item>The first element in the list is isolated
- and the list is split into two sublists.</item>
- <item>The first sublist contains
- all elements that are smaller than the first element in
- the list.</item>
- <item>The second sublist contains all elements that are greater
- than, or equal to, the first element in the list.</item>
- <item>Then the sublists are sorted and the results are combined.</item>
- </list>
+ With the algorithm above, a list is sorted as follows:
+ <list type="bulleted">
+ <item>A list with zero or one element is trivially sorted.</item>
+ <item>For lists with more than one element:
+ <list type="ordered">
+ <item>The first element in the list is isolated as the pivot element.</item>
+ <item>The remaining list is partitioned into two sublists, such that:
+ <list type="bulleted">
+ <item>The first sublist contains all elements that are smaller
+ than the pivot element.</item>
+ <item>The second sublist contains all elements that are greater
+ than or equal to the pivot element.</item>
+ </list>
+ </item>
+ <item>The sublists are recursively sorted by the same algorithm
+ and the results are combined, resulting in a list consisting of:
+ <list type="bulleted">
+ <item>All elements from the first sublist, that is all elements
+ smaller than the pivot element, in sorted order.</item>
+ <item>The pivot element.</item>
+ <item>All elements from the second sublist, that is all elements
+ greater than or equal to the pivot element, in sorted order.</item>
+ </list>
+ </item>
+ </list>
+ </item>
+ </list>
+ <note>While the sorting algorithm as shown above serves as a nice example to illustrate
+ list comprehensions with filters, for real world use cases the
+ <seeerl marker="stdlib:lists"><c>lists</c></seeerl> module contains sorting functions
+ that are implemented in a more efficient way.</note>
 </section>
 
 <section>
-- 
2.35.3

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