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* [glibc] stdlib: fix qsort example in manual
@ 2024-02-02 1:56 Paul Eggert
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From: Paul Eggert @ 2024-02-02 1:56 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e7b90e6e605cf236d4bd79e4930cd6a46f9932c7
commit e7b90e6e605cf236d4bd79e4930cd6a46f9932c7
Author: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu Feb 1 11:52:46 2024 -0800
stdlib: fix qsort example in manual
* manual/search.texi (Comparison Functions, Array Sort Function):
Sort an array of long ints, not doubles, to avoid hassles
with NaNs.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Diff:
---
manual/search.texi | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/manual/search.texi b/manual/search.texi
index ffaadc46f5..db577a5332 100644
--- a/manual/search.texi
+++ b/manual/search.texi
@@ -35,19 +35,22 @@ second, zero if they are ``equal'', and positive if the first argument
is ``greater''.
Here is an example of a comparison function which works with an array of
-numbers of type @code{double}:
+numbers of type @code{long int}:
@smallexample
int
-compare_doubles (const void *a, const void *b)
+compare_long_ints (const void *a, const void *b)
@{
- const double *da = (const double *) a;
- const double *db = (const double *) b;
+ const long int *la = a;
+ const long int *lb = b;
- return (*da > *db) - (*da < *db);
+ return (*la > *lb) - (*la < *lb);
@}
@end smallexample
+(The code would have to be more complicated for an array of @code{double},
+to handle NaNs correctly.)
+
The header file @file{stdlib.h} defines a name for the data type of
comparison functions. This type is a GNU extension.
@@ -183,16 +186,16 @@ in the array before making some comparisons. The only way to perform
a stable sort with @code{qsort} is to first augment the objects with a
monotonic counter of some kind.
-Here is a simple example of sorting an array of doubles in numerical
+Here is a simple example of sorting an array of @code{long int} in numerical
order, using the comparison function defined above (@pxref{Comparison
Functions}):
@smallexample
@{
- double *array;
- int size;
+ long int *array;
+ size_t nmemb;
@dots{}
- qsort (array, size, sizeof (double), compare_doubles);
+ qsort (array, nmemb, sizeof *array, compare_long_ints);
@}
@end smallexample
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